Give her a piece or two of dry oatmeal (the REAL oatmeal -not instant).
Also give her some UNFLAVORED Pedialyte thru a syringe to make certain she isnt dehydrated. Keep checking for dehydration by pulling up the skin on her neck. If it goes right back down, she is fine. If it stays or goes down very slowly, she is dehydrated and needs Pedialyte.
If the diarrhea keeps up for more than 24 hours, she needs to see a vet. If she hasnt had a wellness exam with fecal float and smear - she really needs to be taken soon.