dont worry about chasing then. its always when your not looking that it will smack you in the face.
IMHO (as a woman) if you aproach a girl/woman for the purpose of hitting on her, she will be awear of it and most likely run 100 miles, not because of you as a person, but because you are a man. and contrary to belief quite a few women are scared of being aproached, whats your under lying motive? why her? why now? is she maybe too drunk and an easy target?
theres alot of things taht will be going through her head, and if she thinks your coming on to strong then a million questions will pop into her head.
now in saying this (in defence of other females here) not all women are this way, and this is mainly my opinion and observation of my friends, and also what they have said to me. just dont seek it.