You can try a nice warm bath soak for 15-30 minutes and try to lubricate around the opening with vaseline if you want...it may help. But she would need to be blow dried since it is winter. I'd let her set in the house in a crate for a couple of hours after the bath to completely dry out and to avoid shocking her system with the cold.
I haven't dealt with this, but have read about baths for eggbound hens before on BYC...so take it with a grain of salt.