New rat making weird sound?

I've never had a rat before, but I adopted one from my cl -- she was going to be fed to a snake, snake didn't want her, students protested and finally my teacher offered to give her to anybody who'd take care of her. I'd heard rats make excellent pets so I decided to take her in. She's adorable, pretty young from what I can tell, friendly and extremely active. She likes to run around my room, run back to her cage, run up to me and crawl up my shoulders, and then run away and find other things to explore. Zelda seems healthy, but she makes this tiny... gosh, I don't know how to explain it. It's like a sneezing noise, but not quite. It's halfway between a sneeze and a chirp, and she makes it fairly frequently. My mom thinks it's just her way of being vocal, but I've read that it could be a sign of a URI. I don't see or feel any snot when she "sneezes" but she does make the sound quite often. She also occasionally makes a little grinding noise with her teeth, which I read means she's happy. Since I have no background information on her, but I'm too broke to blow 100 bucks getting her checked by the vet, I was wondering if anybody with more rat experience might be able to diagnose her, if there IS even something to diagnose. My mom says it's just cute rat speak, but I don't want to overlook something that could potentially get worse and make me feel terrible for ignoring. I'm thinking about recording her whenever she starts making the the little noises and uploading it on Youtube. It's like a short, high pitched exhalation. It doesn't sound life-threatening, and she doesn't appear sick, but... I just want to make sure.