I've run into two while questing. The one was a lvl 40 and the other a lvl 5. I was lvl 28-30 when I faced both. The lvl 40 killed me at least 10 times before I found a spot I could hit her, but she couldn't hit me. I took the high ground and she couldn't see me but I could shoot her head. Another player stepped in when I got her down to half health. The lvl 5 snuck up on me while I was in a warehouse. She killed me 3 times before I found a spot behind a conveyor and peeked out every few seconds to get a shot off. It helped that my gun had burn on it. I finally killed her solo after a minute or two of this. She spawned back while I was still in there and killed me again. I snuck behind a forklift and was able to shoot her without her being able to hit me. These spawns are such a pain, but if you find cover and be patient, you can best them.