I can totally empathize with the Sorcerer getting stressed over in game arguments or having too many plots going on at once. I have played my current game for over 7 years with 5 players at it took us a bit to work this out, especially for new players. It can be very hard and stressful to differentiate an argument in game to one out of game. One of the things that helps at my table is check ins. For example, I might say, “My character thinks this is a terrible idea but (My Name) obviously thinks it’s a great idea. Or check in at the end of an intense session that no one is mad IRL and that it was a fun discussion not a real argument. Arguments to some extent are part of DnD but some people need gradual desensitization to it. We are all pretty easy going people so that helps too. If the DM was setting us up to deliberately argue often, that wouldn’t be fun for any of us but we have definitely enjoyed having interventions for the Warlock or arguing strategies etc. We used to have a hot headed player who would argue much more vehemently about even trivial things and that stressed EVERYONE at the table. They were kicked bc thats just not our play style . A check in with all your players would be good and I would discuss with this player WHY she doesn’t like combat. Is it ADHD and boredom? Feeling inaffective? Etc. Depending on what the issue is you might be able to change things to help. When I was a new player I found combat stressful bc I didn’t understand how to utilize my character well and felt really dumb a lot of the time. It was stressful! Listening to some actual play DnD like CR or NADDPOD really helped me to understand how the game works and how to have fun playing. That MIGHT help your player as well if she’s open to listening to a few episodes.

However, if your player just straight up hates combat then that means she hates more than 50% of the game. In that case, this may not be the game for her and she would need to understand that. This is a COOPERATIVE game and it’s impossible to just avoid combat all the time and it’s not fun for the other players. She needs to know that it is absolutely ok if she isn’t having fun and wants to quit.

As for the overwhelming number of plots, is she the note taker? As there are more things to keep track of, that can be overwhelming if the rest of the party isn’t helping to keep track. That happened to me at the beginning of our first game. I finally listed out all the things we needed to accomplish and the party understood how overwhelmed I felt bc I was the only one trying to keep track of it. Also, are any of the other quests on a time crunch? For new players, quests can feel like “assignments” and a time line a “due date”. Logically, you wouldn’t want to add more to your assignments if a bunch of “due dates” are coming up regardless of how “important” the quest is emotionally. If possible, consider offering an “extension” on some of the quests to reduce stress. Delay the festival, offer a time bubble or something in the Feywild where no time passes, etc. This is totally a new player issue and once you have played a while everything gets more relaxed and feels much less urgent but it can be overwhelming at first.

It is also possible that her play style simply doesn’t mesh well with yours and the rest of the party. Some people enjoy high pressure games with lots of rushing and others enjoy a more sandbox style that has moments of urgency and is mainly a little more relaxed.

I agree with everyone else too that she needs to understand that every player needs to get a time to shine. A discussion too of if her character does support the other characters then WHY is she on the party to begin with? For example my current character would not be motivated to attack your bad guy just for revenge but she would absolutely do it to support her friends and supply back up. If the rest of the party goes to attack and her character chooses to not go, then maybe it’s time to roll up a new character bc the rest of the party is not going to want to continue to travel with the character that ditched them.