How long is a good time to wait before asking a girl out after she breaks up with a guy / guy breaks up?

So I have become friends with this girl over the past year and we really hit it off. It's mainly just innocent, friendly flirting but I think she may like me. Some clues that I have picked up on are: She seems to be talking to me a lot more than she used to; she laughs hysterically at most of my jokes; her closer friends seem to enjoy being around me more and are friendlier to me; she tells me very personal things, and I have had it validated by her best friend that she has told me some of this personal stuff before she told her best friend (the girl that validate this for me). So, girls out there, do any of these signs I have mentioned have anything to do with her maybe having a thing for me? Or is the fact that I have a thing for her clouding my judgement and making me see too far into the little things? Anyways, she just acquired a boyfriend today, but these two have been going on and off literally about 4 or 5 times. She has told me that she just like the attention from this kid, but with her doing this I don't know if she really likes him or is back to the same feelings she had for him before she realized she just wanted attention... Overall, I'm pretty sure this will not work out for very long between them and I just want to know how long is long enough to wait after they break up before I ask her out on a simple date, like to the movies or lunch or something. A girl's opinion on this would help, especially one who has been in a situation similar to this. Thanks :\