I'd say chances are good that Snoopy is deaf. My Creamsicle is deaf and I did all the things you did w/Snoopy to test her. If your cats run out of the room when you turn on the vacuum cleaner and she doesn't, then that'll probably tell you for sure. C girl has no fear of the vacuum cleaner or anything else that makes noise for that matter. The other cats scuttlebutt out of the room but she jumps on it. Maybe she likes the vibration, I dunno. And she's the happiest cat I've ever seen and she's so sweet that no one can resist her. The rest of my fur posse seem to know she's deaf and they all tolerate behaviour from her that they don't take from the others, so you might want to observe your other cats around her.

How lucky you are to have found each other. I'm so happy for you both.

Blessings,
Mary