JUST TO CLARIFY
Wendying is when you introduce a newish friend to an oldish friend or friends, and the newish friend moves in on your friends and starts to exclude you. It's fecking awful and it's everywhere. It's called Wendying because there were two threads run at a similar time and in both the perpetrators were called Wendy.
OP this person is not your friend, she is very much a Wendy and it won't stop here.
She has issues around food and she manages them by projecting onto others. You are a target for her because you represent what she cannot have, self confidence.
Because she is so screwed up, she will continue to behave in this way as it works for her. The PA texts, the snide remarks, the excluding you from social occasions.
Sadly, "other" friend sounds like a bit of a drip who feeds her own inadequacies with ridiculous carry on too.
Firstly, don't engage in any more texting about the lunch that's been or the night out ahead. Give yourself a break from that crap.
Secondly, do not stoop to PA remarks or "tinkly laughs" (wtf) advised by some on here, it's unbecoming and immature.
Thirdly, friends are meant to be supportive. I would seriously rethink these friendships, take a step back and perhaps focus more on making better friends or spending more time with existing friends who are genuine.
Your "friend" is a bitch and time spent with her is time wasted.