Braid her hair if she’s a pasture horse definitely braid it
A richer conditioner and some leave in oil/conditioner. Comb from the bottom up so you don't rip or break off hair
You can keep her mane in simple braids after you wash and detangle it. The BEST detangler brand ever is Manely. Look it up online. But it really is the best stuff I've ever used. And it only takes a quarter sized amount to do the job!
Pull it or if its too thin use trimming sheers
I sometimes have the same issue with my Arab mare. I brush her mane twice a day tbh... and when she does get knots I use either detangular or laser sheen. I drench the mane in it and the brush. Using a comb doesn't help much. I just keep brushing it until the knot comes out. I do loose some hair, but it beets cutting an entire lock off and waiting for it to grow back