2.5 year old sleep advice?

2.5 year old daughter and only child. Look at this point we'll try anything. She used to be a semi-decent sleeper. Within the last 2 months it was like a lightswitch flipped and our daughter refuses to sleep without mom in her room. She fights sleep every.single.night. for hours and hours even with mom in the room. We've tried bottles of warm milk, stories, sound machines, light projector of stars on her ceiling, taking her mattress off her bed and putting it on the floor, singing soft songs to her, everything. Her pediatrician recommended melatonin gummies, we've been doing those for about 2 weeks now and still they have zero effect on her falling asleep or even staying asleep. She refuses to sleep without mom in the room, even then she still wakes up sometimes 3 times a night in a furious rage. We have and always have had, a really good day to day routine. She naps fine at daycare, she eats dinner and has a bath and plays before bed at the same time every nite. Her life routine is literally like clockwork. She shows signs of being tired around 7pm and we try to get her to sleep and still it's a battle for hours every night. We're exhausted. My wife and I haven't even slept in the same bed together in 2 months since our daughter will NOT allow her to leave the room at night time. How long does this last? I've heard horror stories on this sub-reddit about some families going through this for upwards of a year. Anyyyyyyyyyyone out there have any suggestions? We're completely exhausted and riddled with anxiety every night before her bedtime.