B.B.
She is testing you BIG TIME!!! Think of HER personality and what ever would not work for her, throw it out... :-)
If you know that she does not have to go potty make her stick to the law of the bedtime... :-) You would let her sit on the potty for 45 min TRYING? lol I am assuming that you are the "softie" parent. I am too... But I learned along time ago (we have 3 with one on the way) that rules are rules. When we say bed... That is it. In the bed, lights out. No night lights, and IF they do get up to go potty then it is a no communication in and out trip. (unless they are sick)
She understands alot more than we think. Sit her down. You AND daddy. Tell her the rules. The rules stay the same for daddy and mommy bed times. Don't worry about punishment stickers (are they really working? )
Take the toys out of her room and make it as dark as possible. (Hard to play in the dark.) Also, make sure you are winding her down for about an hour BEFORE bed. Turn down the noise (radios, tv, etc.) concentraite on books and stories. Then get in gear with the usual routine (teeth,potty, jammies, bed...). Do not use her room as a punishment place. (until she's in her teens.)
Its not about "locking" her in. Its about sticking to boundries. Mommy says NO... THat means NO. Be stern and do not compromise. Make sure she takes sips of water BEFORE going to the bed room. If she says she is hungry, she should have eaten more for dinner. (Yes, it sounds mean... she's 3... But she's also playing you and will come up with anything.) Give her ONE stuffed animal or blankie BEFORE turning off the light.
Then kisses and walk out. Shut the door. And wait. Put a chair so you can see the door and get a book. Sit there and if she opens it, tell her to go to bed. But you do not go in the room. Just watch her climb in bed and shut the door. :-) Might take a bit... And if it starts to wear on you, def. go outside if you need to.
Good luck and hope you find some mixture of something that will work for her and you.