I am sorry to hear about your cat, and also sorry to see you have waited this long for an expert. I have been away and just came online. Do you still want help with her?
I am Rebecca, I am a veterinarian, and will do my best to help, if you still wish to continue.
If the eye is bulging, and the lens has wandered, I am very concerned this could be a tumor of the eye, or behind the eye, pushing it from behind. The only way to know what it is, as you say, is to go through the surgery and have a biopsy done. There is no way to biopsy the eye ahead of time like we would biopsy something on the skin; once we punctured the eye with the biopsy needle, even a tiny one the way we do to test a skin lump or bump, that could permanently damage or blind the eye.
I agree, this eye could be painful. If this were my own cat, I would have the eye removed as soon as possible (maybe you have even already done that!?).
Just ignore all this, if you feel your wait was (understandably) too long. If you have any other questions I can help with, please let me know. Rebecca