Yo so a couple weeks ago I managed to convince my ex gfs best friend to come out clubbing with me and some friends. After spending 10 minutes of my time with her in the clubrun I knew we were definitely going to fuck or at least make out.
night = awesome, end of night = me having sex with her on a beach.
Anyway, in the morning she stated it was a one-time drunken thing and that it won't be happening again. However she has definitely changed since it happened. She definitely texts me more, infact the ratio has gone from 0:1 (me texting her every so often to come out) to 2:1 (her texting me twice for my 1 text)
I recently went to a festival which she also went to with my ex gf. She kept trying to meet up with me secretly as my taste in music matches hers more then my exe's.
Other stuff she did at festival:
1) Moaned a couple times that I hadn't responded to any of the texts she had sent me to meet up/how I was (turned ma phone off to save battery)
2) Made me promise to go see a band with her at a concert some time.
3) Seemed more touchy feely then usual.
Been back a couple days and now the texts are kinda getting flirtatious again.
her: Hows being home?
me: clean, full of food and feeling awesome. u?
her: thats good, I went out last night so feeling tired, hungry and lazy

(She had invited me out for this a week before, I forgot and would have probably been way too tired)
(24 hours later)
me: You best of stopped being lazy and tired now, you owe me a concert!
Her: I haven't

only had 3 hours sleep. I thought you were playing?

I've had a look actually no concerts near us SPAM
I assumed paying had been autocorrected to playing.
me: Dirty autocorrect there, very smooth!

As I've said before, if you want to get all sexist and make me pay for stuff then you gotta clean some dishes. It's only fair
her: haha wasn't autocorrect...oooo depends on what your cooking?
Personally I think this is leading to more sex/her becoming interested in me. For guys with experience in shagging/getting with an ex gfs best friend...how big is the risk here? She did also state several times at the festival when I asked if it would be cool to come drink at their tents that it wasn't but my ex needs to get over it already.