So I have a complicated/long question about how to continue handling this situation. I dated this chick off and on for a couple years...mostly off you know the deal. After we had been broken up for a couple months my exes sister started talking to me about her ex bf. She's defiantly hot but I started talking with no real intentions so I created a pretty solid emotional connection with her and we are very comfortable. Since then I started trying to get with her but defiantly took the AFC route(not enough kino or attraction). She's initiated a conversation about dating a few times saying her sisters only thing holding her back. Anyway we started hanging out more often the past couple weeks so Ive been escalating touching and flirting. Which leads me to my first question...should I continue at this rate or get more pushy and aggressive?

When hanging out there has been two times we've both had friends with us(my best friend and her best friend). Her friends pretty cute but not the target. Her friend showed up at my work the other day and left a note on her receipt which she left on my windshield saying "cutest cashier ever, get at me with a heart". Im pretty unsure how to handle the friend. Should I ignore her completely, flirt lightly or just flat out talk to her? Could this be taken as social proof or will this completely blow up in my face?

If you like the friend pursue, if not don't.

I'd keep some open line of communication with the friend, but in a friendly way (have her as an orbiter) in case things don't work out with your target. But be careful navigating through this terrain as the friend will confide in the target, so don't do anything to incriminate yourself (e.g. flirt).

Remember, pretty much all women talk, even ones who don't particularly like each other. Assume anything you tell her friend is NOT sacred and almost 100% will be shared with the friend UNLESS it makes the friend look bad to the target in some way.

So I should communicate with the friend and keep it friendly but leave it at that? This way I leave that door open if things don't work out with the target but don't ruin any shot I have in the first place?

If that's what you want, by all means.