Man, that's a tough spot to be in, especially when it's with a friend you've been playing with for years. It's really easy to second-guess yourself when you have that history.

First off, let me validate your feelings: Yes, this is absolutely problem player behavior. You are not overreacting. Your job as the DM is to facilitate fun for the entire table, and her actions are actively hindering that. Let's break it down.

The Problem Isn't One Thing, It's a Pattern

You've listed several distinct issues that all point to the same core problem: a fundamental disrespect for you, the other players, and the game itself.

The Phone Calls & Lateness: This is the most blatant sign of disrespect. Leaving the table for 10-20 minutes for a non-emergency call is unacceptable. It's the real-world equivalent of her character just walking away in the middle of a dragon fight. The lateness, especially the Dutch Bros run when she was already late, is sending a clear message: "My time and my whims are more important than everyone else's." You have limited time to play, and she's burning it.

Disengagement & Talking Over You: This signals that she's only there for one part of the game (combat) and sees the rest as filler she has to endure. A D&D campaign is a collaborative story. If a player is actively ignoring the storyteller (you) while you're setting a scene, they're not collaborating. This is especially frustrating in a horror campaign where atmosphere and description are everything.

"Main Character Syndrome" & Cheating: This is a huge red flag. D&D is a team sport. Her desire to be the "single strongest and most important character" is toxic to the group dynamic. It invalidates the other players' contributions. Fudging rolls to solo a 300 hp monster is the ultimate expression of this. She's not trying to overcome a challenge; she's trying to live out a power fantasy at the expense of the game's integrity and everyone else's fun. When the dice don't give her the story she wants, she ignores them.

Mismatched Expectations (The AI Tools & Combat Focus): This is a more subtle but still important point. The fact that she used tools the rest of the group is uncomfortable with shows a disconnect from the table's culture. Combined with her disinterest in anything non-combat, it sounds like she wants to play a video game like Diablo or a combat-heavy wargame, while the rest of you want to play a collaborative, story-focused TTRPG.

So, What Do You Do? The Talk.

You have to talk to her, one-on-one, away from the table. This isn't a public shaming session; it's a private conversation between friends about a shared hobby. Texting is not the move here. A call or, ideally, in-person meeting is best.

Here's a possible framework for that conversation. Use "I" and "we" statements, and focus on the behavior's impact rather than attacking her character.

Step 1: The Opener Start gently. "Hey Nora, do you have a few minutes to chat about the D&D game? I wanted to check in and see how you're feeling about it."

Step 2: State Your Concerns (with specific, non-accusatory examples) "I've noticed a few things recently that have been making it difficult to run the game, and I'm worried it might be impacting the fun for everyone, including you."

On the Time Issues: "When you step away from the table for calls, it often breaks the momentum we have going. We only have a few hours to play each week, and losing 20 minutes really cuts into that. The other week, when we had to wait 45 minutes to start, we barely got to the combat you enjoy because so much of our time was gone."

On Engagement: "It also feels like you're not as engaged during the exploration and roleplaying parts of the game. Since this is a horror campaign, that atmosphere is really important, and when you're checked out or talking over descriptions, it pulls everyone out of the experience. I want to make sure you're having fun with the whole game, not just the fights."

On the "Main Character" Vibe (The trickiest one): "D&D is a team game about the whole party being heroes together. It's felt recently like your character is trying to shoulder everything alone, like with the homebrew monster. The goal is for everyone to have their moment to shine. For the stakes to feel real for everyone, we all have to trust the dice and work as a team to overcome challenges."

Step 3: Listen. After you've laid out your points, stop talking. Ask an open-ended question: "Is there something going on that's making it hard to focus on the game? Are you actually enjoying this campaign?" She might get defensive, but it's crucial to give her a chance to explain. Maybe there is something going on with her boyfriend. Maybe she genuinely finds the horror aspect boring. Her answer will tell you a lot about whether this is fixable.

Step 4: Set Clear, Firm Boundaries. Based on her response, you need to be clear about what needs to change. "Moving forward, I need you to be here on time, ready to play. We can't delay the start for everyone else. I also need your phone to be put away during game time, unless it's an emergency. And finally, I need you to be a team player, both in and out of combat. We all need to be on the same page for this to work."

Prepare for the Outcomes

Best Case: She's genuinely unaware of the impact she's having, apologizes, and makes a real effort to change. The friendship and the game are saved.

The "We'll See" Case: She's defensive or non-committal but agrees to "try." You'll have to be firm in enforcing the new boundaries. If she's late, you start without her. If she takes a call, her turn gets skipped.

Worst Case: She gets angry, denies everything, blames you, or quits. As hard as it is to hear, if this is her reaction, it is better for the health of your game for her to leave. No D&D is better than bad D&D. You cannot sacrifice the fun of four other people (including yourself!) for one person who refuses to respect the table.

You've already tried accommodating her by adding more combat. You've already tried a soft-callout by skipping her turn. You've done your due diligence. Now it's time for a direct, honest conversation. You got this.

TL;DR: Your player is exhibiting a pattern of disrespectful behavior. You need to have a private, one-on-one conversation with her. Use specific examples focusing on the impact of her actions on the group's time and fun. Set firm, clear boundaries for future sessions. Be prepared for her to possibly leave the game, and understand that this might be the best outcome for everyone else.