H.W.
If your intuition is telling you that this is a delaying tactic, then treat it as such. If she 'needs to go potty', put her in the bathroom and then leave. (make sure you've child-proofed, of course). By leaving, she gets no attention, which is a great motivator for this sort of 'game'.
So, imagine tomorrow evening. "Mama, I have to poop!" You go in, cool as a cucumber. "Go potty then." you tell her. Take her to the bathroom calmly, then tell her "Call me when you are done" and go somewhere else. If it were me, I'd be somewhere out of sight with a book, just to keep an ear out. The point of this is no special attention. Make it BORING for her.
Check in on her after 5 or 10 minutes. "All done?" No more words. Either help her wipe, or leave again.
If she's playing around, tell her "all done", calmly of course, and take her back to bed. No re-tucking in, no kisses, because you've already done that.
Nighttime potty gets NO extra attention. If she poops, be low-key and just get her changed, then put her back to bed. No cuddles, no snuggling.
As for the whining, here's the thing: we all know when they are whining and when they are *truly hurt*, upset. Whining-- I tend to ignore it. She knows she's supposed to be in bed. These techniques will help her to understand that YOU understand what she's supposed to be doing, and you are not going to come get her because she hollers. Most kids would just hop out and go use the toilet themselves if there was an urgent need. She might occasionally have accidents at night, many kids do. She won't regress if this happens a few times. However, she might start either helping herself, or staying in bed when it's bedtime. If you keep going in... well, then, she's going to think she has YOU trained!
Good luck, be consistent, neutral emotion, and don't lose your cool. Just be as solid as the earth and take her back to bed.