If she is eating, drinking, and doing her normal, usual behaviours, then it would most likely be just her stomach gurgling. You can hear the same thing if you place your head on another person's belly; the sounds of the stomach and intestines.

Check her litter for any unusual poops (blood, too runny, too hard, a weird colour, etc) and if there is any that concern you, take a photo and show the vet. They love video and pictures because at a vet, a cat is likely to mask any issues bc it's an unfamiliar environment. Also watch for any vomiting, or retching. Id say if all that is normal then it's prolly just the sound her GI tract makes. I can hear the same thing when I place my head on Mickey's belly too haha

If you feel comfortable, I think I made a comment somewhere about taking a cats vitals and the normal ranges, I can try to find it and link it

Found it: https://aussie.zone/comment/11478667