First Ball Python, Need some advice.

[Thomas Steele]

Does this sound like the right size for her age, or is she underfed?

Do you know her weight. That would probably be a better indicator of if she's been underfed or not.

I know I need to take her to the vet. Unfortunately, I kind of spent all my money getting stuff for her and I dont get paid for a couple weeks.

The few times I've dealt with RI there have been bubbles and mucous. I'm not a vet though and based on the conditions you found her it's definitely a good idea to get her a clean bill of health when you can afford it.

Would also explain the aggressive behavior?

Definitely. She's getting used to you and the new environment and being in shed where she feels particularly vulnerable. High stress times for her. Give her some time to settle in and get some food in her and I'm sure she'll be much more relaxed.

Good luck with her. It sounds like shes in an infinitely better situation now that you have her.