LOL Yes this is normal especially if you're petting her on the back. She's hoping for a handsome young male rat to come and sweep her off her paws.
My girls were just in heat last night and today. I've got four girls and their cycles seem to be pretty well synced up. They do get a little crazy! My one girl Buffy, went into heat yesterday morning first and when I pet her back, she peeped at me in the cutest way and her ears started vibrating like a bumblebee about to take flight! It was really adorable. The other girls followed throughout the day and into today until they were all done with it. They were all bouncing around the cage, wrestling with each other, a lot of squeaks going on, and just general hyperactivity. Tonight they're all worn out and sleeping off their hormone filled day.