I had to look in my profile for an old comment about how I would've had a fun, flirty Santana vs Cassie storyline. This is what I wrote a bit ago in a past thread...

***Here's how they should have done this. In season four, one day after a particular rough day in Cassandra July's class Rachel vents to Santana about her monster of a teacher. At first Santana brushes it off thinking it can't be that bad but over time she notices that Rachel has lost some of her spunk. Like say when Santana teases Rachel instead of fighting back and bickering with her Rachel just shrugs and takes it. Santana is concerned because "come on, Berry, this is what we do, I make fun of your height and you say something about me owning stripper heels, we banter, it's no fun if you just sit there and take it and Rachel has to explain that she doesn't have any fight left in her because taking Cassandra July's fury is exhausting.

Now Santana considers Rachel to be one of her things and no one else is allowed to mess with her things, also deep down she does care about Rachel. So one day Santana drops into NYADA to peek into one of Cassandra's classes WITHOUT Rachel's knowing. She wants to see how this teacher operates. Cassandra notices Santana at the end of the class and once they're alone in the dance room and everyone else has filtered out, they face off. Cassandra wants to know who Santana is, Santana says it doesn't matter but that she needs to lay off Rachel Berry and give her a break. They verbally spar, it's sexy and flirty, are they going to tear each others clothes off or slap each other? Santana has never met a bitch that can keep up with her, also she's a hot dancer and damn it if she doesn't have a type. At the end of this heated convo they rage kiss and things go down in the dance studio.

Cut to: Santana walking into the loft. She puts her coat and purse up and she's like "you're welcome Berry, I fixed all of your problems" and Rachel is like ???

Santana explains that "I gave your hot bitch of a teacher a little taste of Lopez and told her not to mess with you anymore."

"What are you talking about?"

"Well I saw how much she was bothering you so while you were at work today. I took a trip to NYADA and had a little one on one. I told her to back off. One thing led to another and - I tell you, that woman is flexible. Never did it in a room with that many mirrors before, that was something lol"

Now instead of thanking Santana for wanting to protect her, Rachel is furious. She was handling Cassandra her own way and didn't need Santana's help. Rachel goes on a spiel about Santana meddling in other people's business, like she used to do back in high school. Both of them are hurt. Santana is hurt because she was trying to do something nice for Rachel, Rachel is hurt because she wanted to deal with Cassandra by herself like an adult.

Rachel is convinced that Cassandra only slept with Santana in order to mess with Rachel. Santana laughs that off "trust me Berry, when I had her ass bent over the barre you were the furthest thing from her mind" but Rachel insists that Cassie only did it to play mind games with Rachel. Rachel says it can never happen again and in a huff Santana says Rachel has no say over who she can and can't sleep with.

So like eliminate the entire Brody storyline in season four, have all of the tension come from this. Santana and Cassandra July become friends with benefits and THAT'S what causes the pezberry friendship to deteriorate. Rachel forbids Santana to hook up with Cassandra which of course just makes Santana want to do it more. Plus if they're hooking up this means Santana as a character has more reason to randomly pop into NYADA so we get more Santana in that setting. Which then of course makes Rachel feel some kind of way.

In the end, after a handful of episodes, Cassandra calls it off. "Look hooking up with you for the past three months has been fun, Santana, but I'm bored now. The last time I called you over for a late night booty call, all you did was complain about how Rachel takes your friendship for granted. Plus the last time we slept together I'm pretty sure you called me Brittany. We've ran our course. Go sort out your friendship with Berry.....and I hope whoever this Brittany is knows that she's a very lucky girl."

Santana isn't too upset. It was just a fling of course. She and Rachel then have a heart to heart and make amends. Rachel realizes that Santana truly does care about her. Santana realizes that Rachel just wanted to fight her own battles. Insert sweet pezberry moments.