http://tinypic.com/r/wsjsdd/8

I'm unsure but i think it may be a 'false widow' spider

This is a Steatoda genus cobweb spider. The S.grossa (US) and S. nobilis (UK) are commonly called false widow. Your little friend may be juvenile, so I can't be specific here.

You could keep her and see if she molts to a defined pattern on her backside.

http://tinypic.com/r/wsjsdd/8

I'm unsure but i think it may be a 'false widow' spider