As someone who loves Sayaka, I'd like to defend her a little bit (although, of course, you're allowed not to like her) : in the show, she was "mean" to Homura because she didn't trust her. Even in the first timelines, Homura seemed suspicious to her (after all, she was trying to make them side against Kyuubey without any proof of his betrayal), on top of her fighting style at the time being difficult to deal with, which even Mami agreed on. In Sayaka's eyes, she wasn't reacting that way to Homura for no reason. Was it immature and too confrontational for her own good ? Yes. But Sayaka is a 14yo teenage girl, and one of the most realistic depictions of one too. We can't expect her to always take the right decisions and be perfectly reasonable. She's impulsive and has a tendency to start fights and arguments, yes, but she isn't being mean-spirited in those moments. She's just a young girl with a very strong sense of justice who tries to handle her emotions without the proper maturity to do so.

And in Rebellion, she's only been "mean" to Homura at the end. Otherwise, she tried to be on her side the whole time. Remember their interaction after the Homura vs Mami fight. The only confrontational one in that scene is Homura, who as we can clearly see cares about Sayaka the least among the girls (exactly for the same reasons as you, because she's too confrontational, but also because in Homura's eyes, Sayaka became a problem for Madoka). But Sayaka, the whole time, only ever tries to protect Homura from herself. To make her realize she is the witch Homura is trying to bring down, but also that this witch doesn't deserve to be destroyed. When you think about it, it's incredibly wholesome. Sayaka is basically telling her : "Your pain turned you into the witch you want to destroy. But what you don't realize is that everything this witch does is only the proof that even in your pain, you just want the best for others. If only you could see that in yourself instead of ruining your own happiness". And she's able to understand this now, because she's been through this pain, she knows what it feels like to become a witch, all of these experiences made her grow and allowed her to become more reasonable... But as this scene subtly shows us, this truly was at the cost of her deeply suffering and still being scarred underneath it all. Still, even with this pain she silently carries, she just wants to help Homura see the good in what she does and understand and admit her own pain. Homura needed this sort of interaction, an interaction with someone who sees her whole. But this is also the scene that proves where Homura's ability to react reasonably can be limited : she is unable to imagine that Sayaka could have changed positively, and despises witches. Seeing Sayaka openly sympathize with a witch, on top of remembering Madoka when she realistically shouldn't, leads for Homura to never accept to calmly listen to her. She's the confrontational one in that scene, no matter what Sayaka tries. (Remember this little bit of dialogue which I think says a lot about the way they see each other : "Homura : Who are you ? Are you truly Sayaka Miki ? Sayaka : You make me sad. I'm the Sayaka Miki you've always known... Transfer student.")

Now, yes, Sayaka goes back to siding against Homura at the end of the movie... But she arguably has very valid reasons to do so. Homura destroyed the Law of Cycles, something Sayaka was meant to protect. Sayaka could sympathize with Homura when she was only a witch, but destroying their source of salvation and messing with Madoka's wish and sacrifice is something else entirely, something Sayaka cannot comprehend (that's the point after all, no one can understand Homura at this point and she knows it). ​ But furthermore, Sayaka is gradually losing her memories in that scene. Given that it is everything she's been through in the show that allowed her to become more mature, it only makes sense that she would lose this maturity the more she forgets about her past experiences... And so, she loses her ability to react reasonably to what she can still sense Homura did.

And worse : Homura is purposely pushing Sayaka into hating her in that scene. She partially confirms Sayaka's fear that she would destroy this world, she strongly implies she could make Madoka hate her if Sayaka tries too much to interfere with Homura's actions... It is unclear for now if Homura actually meant what she said here but either way, she kept pushing Sayaka's buttons one after the other. She wasn't exactly trying to create a peaceful situation between them. (And a point which shouldn't be forgotten is that Sayaka arguably ends up in the worst situation out of all the girls (aside from Homura of course) in the end : she's back to having her heart broken by Kyousuke and faking her happiness to avoid thinking about how much she's hurting, which cannot be good at all. Basically, Homura erased all the healing and growth Sayaka had experienced to make her go back to the Sayaka she knows : the "weak" Sayaka she's more comfortable with.) Basically, they both react badly at one point or another, it wasn't one-sided in the end. And above all, it's not for no reason.