Toddler has been taking diaper off, last night was the first time she did it in bed, help

Basically what the title says, my daughter is 20 mo, she has been trying to take her fiaper off for like 2 weeks, last night she wore a nightgown to bed and when I checked the camera this morning she was butt up, diaper off 😅 I'm not sure what to do as far as training, she is my first. I also have a 2 month old. I am.looking for any and all advice. She is verbal but only has like 20 words and none of them are potty related. She can halfway undress herself. We have potty seats and stuff, just hadn't started with them yet. Thanks in advance guys!