If the bluff fails - let's talk worse case scenario - she gets a sitter in, or just doesn't have a night off
Give it a week and ask her how this is going for her and whether she'd like to reconsider, if it's all been heat of the moment up til now it might not last when she realises how much she's putting herself out. Or think of something else she wants in exchange for access. It will seem horrific to begin with but there's always a way around these things.

tl:dr - call Big Geoff, slip the pigs a fiver not to trawl the Thames for a couple of weeks, job done.
(Darth Foxtrot A one-man army dedicated to making fetch happen, Fri 6 Jul 2012, 9:31, 2 replies, latest was 13 years ago)

Don't forget, my sister's a Detective Inspector these days.

( Monty Boyce, My cheese game is strong, Fri 6 Jul 2012, 9:33, Reply)

I assume that's a euphemism

(Darth Foxtrot A one-man army dedicated to making fetch happen, Fri 6 Jul 2012, 9:39, Reply)

I'll give you one in a minute

( sporters I’m sincerely gratitude to you, Fri 6 Jul 2012, 9:44, Reply)

That's a double entendre

*takes long, hard look at self*
(Darth Foxtrot A one-man army dedicated to making fetch happen, Fri 6 Jul 2012, 9:45, Reply)

You were doing ok until you said slip the pigs a fiver
Monty's forgotten what a fiver looks like
( Peej, Fri 6 Jul 2012, 9:41, Reply)

I've got a £2 book token, will that do?

( Monty Boyce, My cheese game is strong, Fri 6 Jul 2012, 9:49, Reply)

Those cards aren't free you know

( Peej, Fri 6 Jul 2012, 9:51, Reply)