is it called cheating? (respond appreciated, i feel guilty)

first of all, english isn't my native language and second, i'm a girl. so. there's this one girl (let's call her A.) i've been writing with for 2 years. and somehow it was always an on-off thing between us. however, recently she started to send me mixed signals even though she's in a relationship with another girl. we have some kind of sexual attraction to each other (no, i'm not imagining this because when she told me i'm cute, i asked her in a flirty and jokingly way if i'd be cute enough to seduce her and she answered with yes *coughs* i blushed because well i have feelings for this girl and actually i didn't expect a yes there because she always used to change the topic and stuff when i said things like that. well. when i asked her if she meant what she just said, she made clear she was being honest. it ended up with me changing the topic by the way because i was basically shocked lol). so like... we flirt a lot. she's probably just a flirty person in general though so i don't have high hopes. but well. today she told me her girlfriend suspects her of cheating now cuz she readed one text in which i said something and called A. beautiful. at this point both me and A think she's the type of girlfriend once she gets suspicous of being cheated on, she'd definitely check A.'s phone and look for messages when she's not around.

i do feel guilty now even though we were 'only' flirting. and both of us don't know what to do. i told her to delete our former conversations, but for some reason A. didn't want to. i'm just afraid that if A.'s girlfriend really checks her phone, she'll be hurt or even worse, break up with A. and while it's true that i have feelings for A., i certainly don't want to be the reason for a shattered relationship. so. should i try to convince her to delete the chat?