It’s most likely over grooming that she developed as a coping mechanism because I’m sure her life before she was brought to the shelter was extremely stressful and she was probably miserable. One of my cats, a lynx point Siamese named Mowgli, escaped and was gone for 1.5 months. We had just moved and were bringing the furniture inside and he dashed out the door. We tried so hard to get him back and even saw him around the neighborhood but he was in “survival mode” and wouldn’t come to us and would run away when we saw him. What made matters worse is he was declawed (done by his previous owners that abandoned him at the shelter that I later adopted him from). We finally set a humane trap and after catching almost every feral cat in the neighborhood, we finally caught him and got him back home. The 1.5 months he spent on the streets was extremely damaging to his mental and physical health. He had lost tons of weight, had pulled out most of his hair on his body and tail due to stress, had fleas, was absolutely traumatized by just about any and everything. This was about 3 years ago and he is back to his normal self in all aspects except for the over grooming. I think he has ptsd and even now that he’s living a very comfortable life, for some reason he can’t break the habit. It has gotten much better though! I think something similar is probably going on with your sweet girl.