Just because she HAS eaten mediums doesn't mean she should be. Snakes are opportunistic feeders and will often swallow prey larger than they should because they don't know when their next meal will come. In captivity we don't have that problem.

Larger meals often lead to food strikes with snakes, which is likely what you're experiencing now.

I have two males that are right around 1400 grams, just a bit below...which is almost 3 pounds, so slightly larger than your girl, basically same size. They both eat small rats every 10-14 days and are very reliable eaters.

If your girl is still growing she may outgrow smalls at some point, but for now she's better off on smalls.

Also, I noticed you haven't replied to any of the questions regarding a thermostat....do you have a thermostat??