That's pretty much all there is to it.
I've been experimenting with this lately.
I'd always ask before "Do you want to go to X?" and it gives her the oppertunity to come up with reasons not too.. even if she DOES want to go, but then you'll have to overcome that to convince her.
So make it easier... tell her you want to get out of there or head away and as you walk keep talking and just go towards whereever you're going, don't ask, just assume she's following you.
'In that case you're not presenting her with the oppertunity to say No...
Obviously if she stops you and protests strongly then she doesn't want to go, but if you present someone with the oppertunity to make the decision and say No, there's a good chance they will as they are now thinking about it.
Make life easier, assume she's just going with you until she really protests to it, which hopefully she won't.