She might be needing less day sleep and longer wake windows. My 18 month old stopped napping all together now
I would deffs try to push bed time back by about an hour to make sure she's tired enough to go to bed, so later bath and milk. Maybe go for a walk for some fresh air before bed time as well if you get chance? Good luck!
Sounds like 18 month sleep regression x
Sounds like perhaps she needs less sleep/ longer wake windows to build more sleep pressure. Split nights are usually caused by under tiredness. Try finishing the nap earlier or pushing bedtime later. You’ll need to do it consistently for a week+ to see any change though x