Letting the LG do the thinking usually gets you into trouble (or at least ripped off).
So next time, here's what you do:
1. Do some research on PERB - see if the lady has been reviewed before and what kind of service/attitude does she have. Pay close attention to key words like: clock watching, too many restrictions, too new or too inexperienced, inconsistent reviews, overcharging, etc. If the lady has too many negative reviews, then it is no longer a case of YMMV - it's a case of a low mileage provider. In this case, it's better to arrange an appointment with the more consistent providers elsewhere.
2. If you are still feeling adventurous (i.e. a TOFTT mission) - leave your wallet in the vehicle - just bring enough cash in your pocket so you can say how much you're willing to fork out for the service you want (and that's it - she can't charge you more than the cash with you). That forces you to leave and cool off outside. Now if you come back with more cash, then you just gave up your chance to cool off and get away from a potential rip-off situation.
3. If you still went through the session, be sure to let other PERB members know how it was - whether it was consistent with others or maybe better. That way everybody benefits and low service providers can be weeded out of this business. The only way to get these people out is to make sure they don't any more future business - you may not repeat but if you can warn away others, then that cuts off their future income because that's the way these providers survive - by ripping off those who are unaware of their reputation.
I have found that most TOFTT intel found in PERB quite accurate with minor variations (here's where YMMV comes in - and that's simple chemistry or lack of it) - it's just a matter of searching or even sending PM's to the people who have done the reviews to get further details.
Just my $0.02 worth.