I've never flown with a woman with whom I was having a relationship and who has a pilot's licence, but I would say that one should behave just as if flying with another pilot.
And how should that be?
In a single crew cockpit, only one person should be doing the flying - unless specifically agreed beforehand. This business of back seat driving has no place in a plane. Sorry to be pedantic!
I do occassionally let a colleague fly my plane (and let him log it - it is all insured etc for that) and I just sit there and fold my arms, occassionally go to sleep. It's really nice to BE flown, for a change. If he gets a problem, he can always wake me up.
Obviously (when awake) I watch everything, especially when he's doing an IAP. But unless he's actually messed up (e.g. is about to shoot straight through the localiser) I stay quiet.
Some instructors interfere all the time, and drive the PUT right up the wall. It's easy to do that to another PPL too. You can drive a 1000 hour pilot (who would normally be perfectly fine on his.her own) up the wall, by interference. The best instructors say and do very little. A co-pilot should do the same.
As for being unsure of position and having to ask.... well you know what I'd say about solving that one
