21 month old won't settle at night.

[Crinklecut]

Hi, I moved my 21 month old DD2 into a bed in October as she was climbing out of her cot. Since then it has taken her on average 1.5 hours to settle her to sleep. She shares a room with Dd1 who goes straight to sleep ( and always has).
We have tried returning her to bed over and over, but after 2 weeks the number of returns was increasing rather than decreasing (over 200 times a night).
We have tried ignoring her, but she just wanders around and starts disturbing DD1 when she gets no attention.
Now we are sitting on her bed each night, but she still just messes around, wriggling, jumping up, trying to cuddle us, shouting on her sister, and getting out of bed. She still has a nap during the day, usually about lunchtime for an hour,but even on days when she has had longer naps, or no nap, the bedtime scenario is the same.

Evening routine is dinner, calm down time, bath with DD1, stories read byDH then lights out.
DH and I have no evenings now, and would appreciate any suggestions you have.

Thanks

How about a stairgate on her room door? There is no way DS2 who is 22 months would stay in a bed. We still have a deep cot for him so he can't climb out. He would be a nightmare in a bed. He takes 1-2 hours to go to sleep as it is, and gets put to bed at about 6.30 - 7ish.

Thanks for the suggestion, we put her into bed tonight and just shut the door, went in twice to put her back to bed, but third time she put herself back to bed and stayed there....hope it wasn't a fluke!!
Will try a stair gate if this does not keep working.