You may want to link this in the stringray forum, you might get some more help there as well.
From what I've read, once the disc starts curling, the ray is "usually" a gonner. If she's still kicking, she's a fighter.
I wouldn't necessarily worry about the ph too much, at least don't add chemicals as before stated. Right now I'd try to keep the water as pristine as possible. Keep up the water changes. If you add salt, make sure its dissolved before putting it in the tank as it could burn your rays disc.
The disc does look a little chewed, so its possible this is being caused by stress. I would advise keeping the lights off and trying to lower her stress level without moving her to a different tank. I'd also watch the tank as much as possible to see who might be stressing her out. It could even be the other ray trying to breed with her and she's not ready yet, its hard to say. How big are they?
I'd also try feeding her more than just bloodworms, they're more like a snack for rays, rather than a meal. I would definitely try to get her to eat more substantial foods - she should take chopped earthworms fairly easily, from there I'd try to get her onto raw shrimp, tilapia, and other assorted raw seafood. If you can get her on pellets, like massivore, that'd probably be good too.