Simple Balance Transfer Question

[justin220]

Evening all, probably a very simple question/answer, but having never done a balance transfer between credit cards, I'm not sure if this is possible.

Basically my misses has got £x amount outstanding on her credit card (don't want to quote actual figures but lets call it £125), and I would like to transfer it onto mine. However I do not know the exact amount. I know its roughly between £y-£z ( say £100-£150).

Can I just apply for a transfer and click the whole amount (she won't tell me the balance as she isn't wanting me to pay it off).. I'm presuming I need to know the exact amount outstanding

Or, Can I just transfer a fixed amount from her card to mine (an estimate of say £140) or will this not work if I transfer too much? Or will her card just go into credit?

Thanks for any advice

[justin220]

Excellent thanks all