Help. My toddler is waking at 4am!

[wendibird22]

DD1 is 3.5yo. Over all she's a great sleeper. She goes to bed easily and once asleep sleeps very soundly. Up until a year ago (when DD2 was born) she'd sleep until 6:30am or later and we often had to wake her to get ready for daycare. Since DD2 arrived (well actually it was more like DST in the spring that got things wonky) she started waking at 5/5:30am. We bought her a Teach Me Time clock, set it for 6am and requested that she wait for the light to turn green to come out of her room. We told her she could lie in bed or look at books. That was successful for a while (several months at least). Then she started creeping into our room at 5am and sleeping on the floor. We'd escort her back to bed and again request she stay until the green light. She'd cry a little but would stay there. Then she figured out that she could "stall" going back to bed by saying she had to use the potty and she'd play around in the bathroom for at least 15mins and we'd have to put and end to that and send her back to bed. Well, for the past week she's been waking up at 4am, turning on her light and looking at books. Sometimes she falls asleep on the floor with the lights one, sometimes she just stays up, but then she's in our room by 5am and it's getting really hard to get her to go back to bed and wait for the green light. And who can blame her...that's asking a preschooler to wait another hr after she's already been awake for an hour. She says going to sleep is hard and that she can't do it. We can't figure out what the trigger is that's waking her up or what's preventing her from falling back to sleep.

She goes to bed at 7/7:30pm every night.

She goes to daycare/preschool daily and takes a 1-2hr nap. Usually without any trouble falling asleep.

We've tried moving her bedtime earlier and later and the best we get is a 5:30am wake up time. If we try earlier she lies awake for 30-60mins and so earlier really ends up being the regular time anyway.

She's pt'd but not at night so she wears a pull up to bed. She knows she can get up to use the potty any time during the night and often does at some point during that 4-6am time. Her pull up is always wet in the morning. Not sure if a wet pull up or the feeling of needing to go potty is waking her up. I've asked but she doesn't know.

Yesterday (after having been up at 4am and unable to fall back asleep) her teacher said she was emotional throughout the day and crashed at naptime. So I'm definitely worried about this is becoming a bad pattern leading to sleep deprivation (hers in addition to mine!).

We have thought about dropping the afternoon nap but part of me thinks she still needs it since she doesn't fight taking a nap.

We have thought that maybe the wet pull up is waking her up and wonder if we should wake her during the night to potty or try some type of overnight pull up to keep her feeling drier.

We have thought about starting a behavior/sticker chart to reward her for staying in bed with the lights off until her clock turns green (and we'd likely set that clock back to 5 or 5:30 and slowing adjust it longer because I think we have gotten so far from 6am that it's too much to expect of her even though it wasn't when we started with that clock).

I could really use any other ideas or suggestions.