<human>: Can you provide a brief rundown of the text in within 3 sentences?

I [26F] became really close friends with Jane [26F] in the summer, and with her came her best friend Sarah [26F]. Jane recently got dumped, and in an effort to support and care for her, Sarah and I teamed up and worked together for the past month or so to make sure she was in a good space mentally (it's still pretty rough). In that time, I realized I really can't stand Sarah. She is too nice. I am not nice. She talks in a baby voice all the time, she is clingy and she won't leave me alone. I told Jane, even though I felt so bad doing it, that I didn't like Sarah. She understood, and said she's noticed all the things that drive me nuts and doesn't blame me for wanting distance. I ignored Sarah for a while. Sarah and Jane stopped talking, too, for a little, because Sarah has been making the situation between Jane and her ex worse, repeatedly. I almost get the vibe that Sarah is in love with Jane...

ANYWAY. My main issue here is that I need to tell Sarah that I can't do this anymore. She texts me, still, all the time. I know part of it is my fault--I'll go a week without responding to her, but then I went to her birthday party two weeks ago and acted like nothing was wrong (for Jane's sake...I didn't want to be there, trust me). I know I'm being shady and I want to come clean, but I don't know how to. The bitch in me wants to be like "yo...stop. I can't do this". But as someone who knows Sarah is just a nice person (to a nauseating fault) and only means well and is just super annoying to me, it's hard for me to jump down her throat like that. 

Ignoring hasn't helped really, and in the long run is probably not nice either. Pleaseeeee help, I've asked so many people's opinions and everyone has told me to suck it up basically, but I'm the kind of person who will explode if things get pent up too long.
<bot>: my best friend's best friend is super annoying to me and won't leave me alone, how do I kindly let her know I need space?