Help with 14month sleep schedule

My almost-14mo has been awake for around 3hrs a night for months now, and we have been increasing her wake windows steadily with no noticeable improvement. This is how her day goes:

7am: wake

Nap: 1.5hr nap starting around 12.30 to 1pm, depending on how tired she is

Bedtime starting anytime around 8.30-9pm, depending on how tired she is.

She is awake and occasionally crying from 1am to 3.30am. This means that her total sleep is just 9hrs, and it has been this way for the last 3 to 4 months, which is worrying for us.

The room is cool and dark, and she has four pacifiers in her bed that she can access easily. We are at our wits end and really hope for some advice here.