Rubbing her butt on the floor, also called scooting, can be an indication that her anal glands are full and need to be expressed. If they are full and she cannot express them on her own, they can become impacted, infected and worse case scenario rupture. If she is still scooting have the vet empty them for her.
My Shih Tzu's do that. It's common in small dogs who cannot empty their Anal Glands by themselves. Your Vet will do it for a small fee of about 15-20 dollars or they can show you how to do it at home. I let the vet do it. They squeeze out the fluid. Your dog will probably have to go have this done every month or so. It's really up to you to determine when your dog starts to scoot again. They can get infected so I would take your dog soon.
stand your dog, place a BIG paper towel over her butt.put a thumb and index finger on each side of the anus, but slightly "behind" it, kind of like a baloon you just blew up and are fixing to tie off, the anus should be in front of your thumb and finger, which will be at the 3 and 9 o'clock position. ( actually if done right, the anus WILL kind of look like the end of the ballon) Give it a squeeze as if popping a pimple, and the result should be the same, which is why you are covering the entire area with a paper towel.The amount varies, but it's like a glob of toothpaste you'd have on your toothbrush.maybe a bit more, but it's not going to be enough that the towel can't sheild. Save your money and do this yourself. oh yeah it does stink a little sometimes fishy-poopy