Any time a dog undergoes a sudden change in behavior, it's best to have it looked at by a vet. Chloe may be ill--and if she's developed a pyometra, it could be life-threatening so the sooner you get that vet appt, the better.
If physical causes can be ruled out, then perhaps the vet can help you figure out what's going on with her. It may be something to do with weaning her pups, but most of our members are very pro-spay/neuter, so won't have a lot of experience to share...
Good luck with Chloe, mrosier.
I hope you can get some answers from the vet