I agree with Sophie, this is definitely down to her not napping in the daytime. Her wake windows are just as important as how long she’s napping for too. She should be awake for 3.5 - 4 hours in the daytime between her naps. Have you got a routine for putting her down at night? xx
A friend of mine used to tell me “sleep encourages sleep”. When baby naps during the day, where are they? What’s going on in the house? Have you tried contact napping in a sling during the day? Not ideal, but maybe get a longer stretch of sleep x
I know this sounds ridiculous because you would think because she barely sleeps during the day she would sleep at night, but thats not how it works. The recommendation at this age is 2-3 hours in total of nap time during the day, the more she naps during the day the better she should sleep on a night. Overtiredness is the worst for getting them to settle. Id also aim for a 7pm bedtime if shes waking up at 7am, 12 hour day, 12 hour night x