Question about proper weight

[200xth]

I am somewhat afraid to move her up to medium rats (there seems to be a big difference between the smalls I have and the mediums I have), so I'm not sure what to do at this point.

You don't need to move her up. You can sustain a female on small rats (65g to 75g) forever if you want.

There's guidelines for this, and people do things slightly different. You'll have to pay attention to your snake and see what works. Some of them seem to like smaller prey more often, some seem to prefer bigger prey less often.

To a degree it's trial, error, and observation. But don't feel you have to move up in size if you don't want to.