You are trying to be a good friend and that is to be commended, but you are also in a tough situation trying to help your friend as well.
You are sort of caught between a rock and a hard place in trying to help your friend and you describe a friend that has a lot of emotional issues that she is dealing with.
Knowing that she has had an eating disorder, but is looking healthier now that she has, does indicate that she may have depleted her bones of calcium and that could account for the number of injuries she has had and the damage to her spine.
I am not surprised that you feel she may not be honest with the athletic trainers but on the other hand, they have eyes and should be seeing something that is going on with her.
It is disturbing to think that they are not being helpful to here.
I would suggest that you try and talk with your friend and tell her how concerned you are about her, her spine problems suggest that she see a spinal surgeon for an evaluation. Let her know that you understand her fears and concerns but if she ignores the pain and problems, she will do serious harm to her spine and it could cripple her for good.
Spinal problems will not get better on their own if they are not properly treated and cared for.
Do both of you live in a dorm or does she live in the dorm on campus? If so you might try and talk to the RA on her floor and express your concerns as well. She might be able to help you or guide you in the correct direction to go to help your friend.
You are walking a tight rope in that if you interfere to much, your friend may turn against you and you will lose the friendship for a time or maybe even for good.
On the other hand, if you need to really take some intervention on her behalf and you don't, the consequences for your friend could be dire, and you would have to live with that as well.
It is a decision that you need to make on your own as to how far you want to go to help your friend.
I would start by talking directly with her and maybe expressing your concerns to the RA if she lives on campus in a dorm.
then you may need to decide how much further you want to go.
Good luck and keep us posted on how things are.
Fran