Snake Feeding Question

[currytoys]

I am a new fairly new snake owner. I purchased a Female Red Tailed Boa 6 months ago and I couldn't be more happier with her. Extremely tame and no issues at all with temperment. I was told she was about a year old, approximately 3 feet 1 inch long when I purchased her. She's about 3 feet 6 to 7 inches now. Here's what I am questioned about: She snatches a thawed out frozen mouse the second I put it in front of her not picky at all. I've started feeding her once a week and then I noticed there hasn't been any feces in her cage. This concerned me and made me wonder if I was under feeding her. I went to 2 medium sized mice a week and I still rarely see any feces. I don't want to over feed her or under feed her. I would prefer that she not get excessively big from over feeding but I want her to be happy. I've heard different stories on how big of a mouse I should be feeding her & how often. I am a little confused. Could someone with more knowledge help me/inform me on proper feeding without going excessive? Thanks and any info I appreciate!!! The reptile Store that I bought her from has not been helpful. I think once the sale was complete they didn't really care. Sandy in St. Louis, MO.