18 month old routine

I need some advice on my 18 month old daughters routine. Shes been waking up between 5am-6am for the past 3 months. I thought it was a transition at first from 2 naps a day to 1 long nap. On a typical day she would wake between 7-7:30am, breakfast around 8, nap at 10am for 1hr. Wake 11am. Then dinner at 12, back to bed at 2pm. Nap for 1hr, wake at 3pm, snack, tea around 5pm, start bath at 7pm in bed by 7:30pm. I changed her to nap from 10am-12pm which was working she would wake at around 11:45am bed for 7pm and wake in the morning around 6:30am which is fine. Now, my 3 year old daughter is in morning preschool from 8:30am-11:30am so I have to leave for school around 11:20. I can't put her to bed for a 2hr nap at 10 because I have to wake her so we cab go get her sister. So I've started putting her down at 12pm hoping she will sleep a couple of hours but nope I get 1hr 10mins if I'm lucky and she's gone back to waking up at 5:30am. The timings aren't right and it's really bugging me I can't get it right. I'm exhausted she gets up so early I have to take her downstairs straight away so she doesn't wake up her sister. She's not mardy at all until around 2-3pm she's such hard work to get through the rest of the day. I am a SAHM their dad works full time so it's just me dealing with it day in day out and it's so hard. I need to get it right. I've looked at the average awake windows etc for her age. So anyway what are your 18 months old routines and how did you get there. Any advice will be greatly appreciated.