UH oh...I took one look at the pics, and thought she's nursing! Too thin around the middle, and a voracious appetite = kittens. If you put catnip down near where you can see her when she rolls around, you'll be able to tell better if she's nursing, and how many. It will be obvious which nipples are being used, so it also gives a good guess on how many little ones are under the porch. Then it's time to get that trap, catch mom, then fish the kittens out by using a good flashlight, and a butterfly net. I'd work fast before she up and moves them to another nest. P.M me if you need tips, or help!