You know you can't fool your mom on everything. You have tried that before and you always end up tripping yourself up on this or that and then blundering again when trying to cover up the mistake.
No, you will have to fess up to some stuff. But which? And how to keep the rest hidden?
Well, start with the honest and hope for the best.

"Things are really different here and I am way confused, but I'm told I should do pretty well here."

"You are safe?"

"Well, as safe as I can be with all these vore around me. But they have all sorts of protection against digestion, so it's not too bad." Given that it's at least a 1/3 chance you will be nutrition within a year, it's not too good either, but Mom needs the assurance more than you do. You aren't exactly cool with the idea of being food of course, but it doesn't freak you out like it does Mom. Having seen Rickie, you wonder if you have a touch of the same thing.

"How is your room? They said you would have you would have a roommate. What's her name? What can you tell me about her?

"Rickie. Ah, Rickie is very friendly." [way too friendly, actually] "We should be able to work out any problems, and if not, I may be able to change in a week.
"Rickie" [Now when did you start calling Rick Rickie? Did that attack on you actually impress you favorably? Well, for the moment, you had better ask no questions. Explaining what a boy was doing in your room is beyond you at the moment.] "is ... human." [Yes, that might distract Mom from more embarrassing things.] "It seems there are a lot of them here. They're kinda weird. They don't mind being eaten."

"I've heard too many boys try to make that excuse."

"Well, it's true here. In fact, Rickie almost forced hi..her way into my belly."

Ops, that practically gave away two secrets at once. Going on past experience, she will catch one. You have having a little trouble deciding which one you hope she misses.