You will most likely be the rebound guy to proceed seriously with this chick.
So I'll say that if you cannot completely turn your emotions off and just have a fun little fling with this girl you are going to get burned badly by her while she uses you to get her emotions stable and then goes after a man she really wants when she gets all that she needs from you.
And no I'm not saying she'll use you totally as an emotional tamp0n in an obvious way where you only get to talk to her while other guy's touch her but you'll think you are in a healthy relationship with her and that her words actually mean the great things they say to you but they don't if her breakup hurt her enough.
If it was a really hurtful breakup she will use your presence as strength to get over that and then leave you brutally when she feels confident enough to go begin the search for what she really wants and her mind is clear thanks to all the effort you put in.
This rebound crap is horrible because she may fvck ya, she may suck ya and she may seem profoundly interested in you and do all this good stuff for you regularly but when her emotions surrounding her ex settle she'll begin to feel bad about being around you and not know why and the reason she will feel bad is subconsciously her brain knows that she used you to get over her ex and once those emotions settle that subconscious will influence her feelings towards you as something to discard like the ex discarded her due to her bad feelings surrounding what the ex did to her.
You become a symbol of the ex in a way for her to reclaim her lost power through by dumping since you became the symbol of recovery from her ex and are thus tied to her ex whether you like it or not.
And all of this gentlemen is why you want to avoid the rebound guy situation at all costs as far as serious relationships are concerned anyway.
