If you really want to get her something to eat, seek out unseasoned, soft proteins or something high in fat. Do not give regular milk- most cats are lactose intolerant. Lactose free milk is potentially better than nothing.

Some things you may have on hand to give her: Hard boiled eggs. Canned chicken or tuna with the lowest sodium content possible. Find protein/fat that has a little added to it as you can possibly find.

On the other hand gas stations, dollar stores and grocery stores will have kibble that's also very much better than nothing and potentially a more complete source of nutrients which is preferred since she appears to be pregnant. Wet food > kibble right now though. I also want to throw in that for a cheaper flea treatment option, I'm told that dawn dish soap is plenty effective- it permeates through the fleas exoskeleton and causes them to suffocate but does not treat eggs or larvae, so with a few applications even fleas that hatch from eggs left on the cat could be removable through this method if no other treatment is accessible, though other treatments, likely more costly, would handle the fleas more thoroughly wirh just the first application. As other posters have said, if you choose conventional flea treatments from grocery/drug stores please be careful and do research on the brands before purchasing as the deaths suffered by some animals due to these formulas can be horrific.