Ignore her or pursue her?

in my opinon, you say 'that's it'. This girl is using you to fall back on, and you deserve better than that. It shouldn't surprise you that she gave you her number - she cheated on you before, she'll have no qualms doing it to someone else. Is that the kind of person you want to be with, and would you ever be able to trust her again? You've been the one who got hurt - don't persue her and do the same thing to someone else. If you try and base a relationship on bad karma, it never works out. Do you see the pattern? When you wanted her, she didn't want you. When you no longer wanted her back, that's when she came running, tail between her legs, because her 'affair' wasn't all it cracked up to be. Now that you want her, she's with someone else again (although still trying to keep you as a back-up plan). She sounds like the kind of person who fears committment and gets bored when a relationship loses its original excitement. She burned her bridges when she first threw you away.