<human>: We can call my bestfriend "Alex" and we'll call her boyfriend "Steve"

I'll try and keep how we met as short and blunt as possible. 

Alex added me on Facebook sometime ago shortly after I split with my ex, she had intentions of flirting and eventually gave me her number and continued said flirting. At this point I had no interest in a relationship so each time Alex would ask me to be in one with her I'd reject the idea. 

Fast forward three years and she gets together with Steve, she still spoke with me a lot; everyday in fact. She never changed her attitude either. 

She started coming around to my house often, Steve of course knew. At this point I was friends with him too (not close) 

She's liked me for a very long time pretty much, and there's no denying I've liked her. But last night she was very touchy feely, rubbing her noes against mine, cuddling, all of your generic boy/girl stuff whilst in a bedroom combined with infatuation. But them she kissed me, I initially stopped her and said we shouldn't do this, she agreed; but it continued. A lot. Proper full on kissing for hours on end and hen she proceeds to declare her feelings for me and how they've always been there. 

Look, the idea of me being a product of cheating is absolutely tearing me apart as I'm extremely against it. I have absolutely no idea what to do with the situation as she's still talking to me like she always does (flirtatiously, lots of kisses, yeno..) 

Can someone please offer me some advice on the situation, thanks very much.

Can you provide a brief overview of the text?
<bot>: Bestfriend and I made out a lot, she has a boyfriend but still very clearly likes me... Feeling's mutual. Not happy about being a product of cheating. Need advice.