Hi Nyte, welcome to Redtailboa!
It is unsafe to feed live prey, as you do know, so if you do you have to watch her kill it and eat it to make sure that the prey doesn't hurt her. check out BW's post on his first pygmy rattlesnake to see what can happen to snakes fed live prey. You say that she has been bitten, check all the bites to make sure that the wounds have healed. There is a risk of the wound turning septic, which would certainly not be to her benefit, and maybe the reason why she is so agitated. Snakes are quite sensitive to wounds.
There may be other reasons why she is so aggresive. She may have distemper or some other temperamental problem. You did say that her origin is unknown, so that in itself is a problem. If she was a wild-caught snake, among which distemper is an issue, you may face a whole lot more difficulties (like parasites) than just edginess.
This is a possibilty. Maybe this
BCI is aggressive by nature. Perhaps the reason why she was so "docile" was because she was shedding or sick. Has she shed recently? The colour change in her skin might be due to a shed. Then again, she was eating well, so that is unlikely. Or perhaps she is sick now. That, hwoever, might led to listlessness rather than increased aggresivenes.
Still, you're right, get her to a vet. He can give her a total checkup and clear up any problems she might have.
Hope this helps and all the best with this lovely snake!
[addsig]