If your cantnap is time sensitive, as in you need it a bit earlier than you think she will take it, then you can wake her a bit early from her long nap so that the timing will work.
And, IMO there is no need to fear AP. I know it is supposed to be a big no no but a few instances of rocking a child to sleep (as an example) is not going to cause problems. I have actually insisted that we KEEP using things like rocking now and again because there are times when I need DS to sleep by being rocked (on flights for instance) and if he isn't able to go to sleep that way then I am in trouble! Sleep tools can be your friend!