I am a sorry excuse for a breeder, I guess...I have never weighed a snake I thought was gravid. I rarely weigh any of my snakes, unless a) for some reason, I am curious, b) I need to calculate a drug dose, c) somebody asks (this would include snakes that I am selling when I expect somebody to ask the weight, ie BPs). Most of the pythons species I have bred, I have been able to make an educated guess on them being gravid...provided I consider the idea far enough into the process, and take the time to really look. I've never been particularly good at palpating eggs - I tried it, unsuccessfully, a few times on gravid monitors, but I don't recall ever trying with snakes (I guess I just figured I was no good at it, so why waste my time). The other part of that is that I minimize handling when I suspect an animal is gravid.
All that said, Clay is correct - womas will copulate pretty much any time they can. Out of season breedings are typically infertile; but if you cycled them, there is a chance. Gravid pythons will regularly lay tipped on one side, or even upside down - womas are no exception (though there CAN be exceptions, lol).
You say she has eaten one medium rat in the month that you have had her...is it still in there? A pound, on first consideration sounded like a lot to me...but I have since considered the feel of a clutch of eggs, the weight of an average rat, and the approximate weight of a breedable female. Certainly not out of the question. As for looking swollen, some girls hide it better than others, lol. In many cases, if you don't know what to look for, it is easy to miss until just before deposition. (The visual cues are sometimes fairly subtle, but the more familiar you are with the animals, the easier it is to observe).
Good luck.