Do I keep her or do I move on? Advice please...

The rescue may agree to let YOU find the next adopter. Especially if she stays in your care until the right match is found. If they don't have to pay for her care again, that allows them to focus on other horses.

Very good idea!

Yup, you are answering your own questions, because if you have to ask that, then you probably aren't. Doesn't make her a bad horse, or you a bad owner, but she just sounds not to be the right horse for you just now.

It can probably be saved, but it would probably mean her going to a trainer to reestablish her basics, then you working with a good trainer so they could help you become an assertive leader for her.

It's a shame when you get the right horse at the wrong time, but it happens, and rather than make both of you miserable, it may be best to cut your losses and invest in a horse who doesn't need so much from you.

The changes in diet may be helpful as well as getting a trainer to work with you both.

However, in the end it will still be you having to deal with her. If you don't feel like you can be the boss mare, you should sell her. Otherwise she will get more and more difficult to handle. You want to be able to move forward in your horsey education and have fun. Biting, bucking and rearing are so, so not fun.

I think you mentioned she was a rescue - will the rescue take her back to be re-homed?

And think older horse for the next one. My first horse was 17 and she's worked out great.

Sorry - looks like I missed a bunch of posts! Returning to the rescue sounds like the best solution. It would be impossible to ever enjoy a horse you didn't feel like you could trust.

Best of luck to you!

If the rescue says she should be returned to them-then return her & let them know you would still like a horse, but somethng much calmer,hopefully w/enough training to be rideable & safe. There are lots of horses out there & horses are easy to love, especially if they are being good partners to you.

Might as well be the Strategy doing that, I've heard before that some horses get hot on it.
The decision is yours. You at least won't have to worry about finding a good home, the rescue will take care of that. If you have your doubts, mainly about yourself, it seems, which is a good thing, I may add, then give her back and find a seasoned horse you can enjoy and learn from. If you feel up to scratching the Strategy and do more groundwork, which, done right, with time will give you confidence, especially if you get help doing it, then try

The only issue is that the rescue itself is where she got so underweight and poor of health. They did not give her the attention or care she needed. I'm afraid that returning her will doom her or she will get unhealthy again, which I definitely cannot let happen

The only thing you can do is talk to them and find out what they think

Well, then change her diet(beetpulp, ricebran and a vit/min supplement instead of the Strategy), find help with working with her and see what happens. Talk to the rescue to find out what the possibilities are.
Doing groundwork and being able to control her will boost your confidence and make her way more cooperative too.