Am I really to do PU/pD if she isn't actually crying until I leave.
Nope! PUPD (or PD in your case) is only meant to be done when LO is crying and needs help. If she is not crying, then you need to just step back, not make eye contact or engage her, and wait til she needs you. If you are doing PD with a LO who is not crying you are still a prop and she isn't learning anything. It is also much more likely to become a game.
My gut would say she's OT or has hit her second wind by the time you are putting her down at BT, as that's a really long day for a 12mo old on one nap. This was classic for my DD... she would chat and play and just generally faff about in her crib when giddy OT. It's super frustrating. Were you ever able to try the earlier BT we talked about before?
I know she was not well the last time you posted on your NW thread. I'm assuming she's feeling better now? How are the nights going?