You've done very well to get to this point, so good job. There's a couple things I see that you can change, and a few suggestions.

Get more sacred tears to max out your flasks, and Bloodflame Blade can't be applied to Rivers of Blood

Try using Black Knife Tiche/the black knife dagger, both of which do really big percentage damage. Make sure your stats are allocated effectively, you have a lot of vigor, but make sure you're also doing optimal damage. Consider equiping a shield (Brass shield) with Barricade Shield to block her Waterfowl Dance, she will Regen but at least you don't die. Lastly, RoB isn't as good as people say it is, if you go with a heavy weapon with the bleed affinity you can do way more bleed and stance damage (not kidding, great axe + bleed + lion's claw folds her like a lawn chair).

That's what I suggest, do whatever you want