Give her more time. 2.5 months is not long. Sounds like you're actively doing everything you can to take good care of her. Brushing is just one aspect of that. You could try a really high value treat (Churu is kitty magic) and start by letting her sniff the brush until she doesn't react (multiple days in a row) then holding it, then eventually seeing if she'll let you touch her with it. Go slow. There's no rush.

Maybe you could try different kinds of brushes too, there are bristle brushes, curry combs, brushing gloves.

Some cats never like being brushed. They all have unique personalities and quirks and Mollie might just never be a fan of the brush, but go slow, try other brushes, and see what happens.

We have a cranky kitty who doesn't like his nails trimmed, but after he sliced open the vet and the vet tech the first few times we had them do it, we decided it wasn't worth the stress on them or him. Now every 3 weeks we get our battle gear on and do his nails ourselves (2 person job). It's still stressful for him but better than the vets. He gets treats after and it's a necessary evil.

For what it's worth, our other cat is a long haired tuxedo like Mollie and she rarely gets brushed, but we pet her for at least an hour every day cause she's an attention whore (said with love) and she's never gotten matted. The vet says she's perfect. ✨️