So the question is; How long before you bail and move on to the next girl?
Girls love company/attention at clubs and just because you're getting "on well" with her doesn't mean it will come to anything if you hang in there till the end of the night, you might get the number then but we all know that numbers at clubs aren't that great anyway. So the next option is to wait 10 mins and make another attempt or try to get a number close at least before moving on or just go for a number close and move on.
Girls love company/attention at clubs and just because you're getting "on well" with her doesn't mean it will come to anything if you hang in there till the end of the night, you might get the number then but we all know that numbers at clubs aren't that great anyway. So the next option is to wait 10 mins and make another attempt or try to get a number close at least before moving on or just go for a number close and move on.