Dd2 is nearly 18 months and shares a room with her big sister, who is 4. This had been working well, until the last couple of weeks when dd2 will not go to sleep, so they both go at about 7.30 and then there is mucking about, and then dd1 falls asleep (she would go within about 10 mins if dd2 wasn't keeping her awake). Putting dd2 to bed first used to work, but now she either won't go to sleep, or wakes up when her sister comes up. She is happy to have a longish nap in the day, 2-2.5 hours. Is it time to curtail this? Or is it developmental? It's 9.15 and she is still awake, having gone to bed at 7.30. Dd1 isn't getting the sleep she needs. They have to be up at around 7 to get to nursery, so it's not as if they can sleep in. Dd2 wakes before 7 in any case...
What time does she nap? My dc both had to be awake before 3.30 otherwise they wouldn't go to bed.
I would try cutting down her nap length if she isn't sleeping too late in the day. Both of mine needed a cut of point for naps otherwise bedtime was a pita. Try cutting it down to 90mins maybe and see what happens.
She is normally up by 2, but probably worth cutting it back. On nursery days she has shorter nap, doesn't seem to make any difference...but maybe doing it several days n a row? If it doesn't make any difference might as well have 2 hours off in the day