I am so sorry to hear about your problem. It sounds quite painful and rather upsetting.
It's clear that you are ready to stop BFing and at 15 months, there's no reason not to, but can you stop her biting you in the meantime?
What do you do when she bites? When my DD started biting me, the feed was swiftly stopped and she was deposited not too gently on the floor. It didn't take too long for her to realise that biting me wasn't worth the hassle.
On the topic of stopping, it really depends how long you are prepared to take over it. Have you already cut out any of the daytime or nighttime feeds? Obviously, it is easier to stop gradually, both because it allows your supply to drop gradually and also because it allows your DD to gradually come to terms with no drinking and to realise that she doesn't actually need to any more.
Cutting down midnight feeds first, followed by midday ones, the morning feed and finally the bedtime feed is probably the easiest way to do it.
However, if you want to stop more quickly, there are ways to do it. Replace the Bfing itself with a cup of warm milk on mummy's knee with a cuddle. Make sure that other aspects of the bedtime routine remain the same and, if necessary cuddle her to sleep to start with. You can worry about getting her to go to sleep on her own at a later stage.
It will be tough for a couple of nights, but don't worry, it won't last more than that. She will soon realise that she doesn't need to BF for either nutrition or sleep.
Good luck with it.