A few months ago I started hanging out with this girl I met quite a bit and we became close friends. She started inviting me to her house pretty frequently and I kind of developed a crush on her. We play video games together, go out to eat, cook together and watch movies together, etc. I have met her mom, her dad and her siblings. We even went on a date to the movies together. It was pretty casual but she had fun and said she wanted another one. She also told me that she did think she liked me, but she is demisexual and she has to be closer with someone and trust them to be romantic. So we were spending like I said a lot of time hanging out.

Then we were told her brother was moving in with her. And things immediately got weird. Let's call her Lynn. Well, Lynn instantly changed things up. She'd been flirting (as she said casually and for fun, that she had a flirty personality) with my nesting partner also. She said he cannot flirt with her around her brother but I can. That upset my nesting partner quite a bit but he said basically okay but I don't want her to flirt with me. He never even moved in.

The next day while i was at work she told me she did not like the idea of me talking with a potential partner I've been talking to. I said that potential didn't do anything to her as she had never met them. Lynn got angry and said she was single and I had NP and potential. I said I had made my intention clear to her and she said she was not ready. Her being single was a decision she made. She then brings up that she wanted a possible triad with my np and myself....and she thinks it was "not allowed." I explain it is 'allowed' if it happens organically and if she does like np she was open to pursue him as well. She started flirting with him even more heavily

. We went out to a nearby town a few days ago and went to a gaming store (her request "randomly") and got coffee and food with my np (let's call him Stan) Stan drove us around basically all day and stopped off for dinner. Lynn was being very flirty and then said she had the best day she's had in years. So Stan asks her about the last time she had a day this fun and she thinks on this and mentions a past friend with benefits. The next thing we know is he's (former FWB) contacted her "randomly" and needs help on a mental health crisis so she goes and spends THREE DAYS AND NIGHTS with him to help him. She states nothing happened sexually since that would be taking advantage but she also went out of the way to tell me she slept in his bed. And promptly told me she is emotionally unavailable and afraid of being hurt and she can't pursue me romantically because she is afraid to be hurt again or damage our friendship. Then last night she told me she wasn't sure if she had ever liked me and I misunderstood her. Which to me is gaslighting. And she keeps cancelling plans to hang out. To make matters worse my np asked her what boundaries they would have in regards to flirting because it was allowed before and she said it was still allowed and never said she's not still interested in him. It seems almost like a bait and switch situation.

Side note: I say "randomly" because I told her my potential and myself and NP were scheduling to go to a gaming store together. We made sure to go to a totally different town for the game store as well as my np sat in the car and didn't go in because that behavior seems very cringe.

Edit to add: I'm asking is this gaslighting? Is it wrong for Lynn to go after my nesting partner? What caused this weird and sudden change up on her end? Should I stay friends with someone who's clearly lying to me?