Is this reasonable and fair to allow certain house guests to bring well-behaved dogs (one of which is a seizure alert dog)to visit, but to not allow poorly behaved dogs to visit?

My mother-in-law lives 15 minutes away from us. She is upset because we told her she can't bring her dog to our family dinner tonight. The dinner invite was sort of last minute, but we thought it would be nice to have everyone over.

My parents and my sister are visiting with their dogs, a 5 year old Aussie and a 12 year old border collie. My sister's dog (the Aussie) is a seizure alert dog, and my parents came up Friday. My parents and my sister always visit with their dogs. My sister must travel with her dog obviously. Both dogs get along great and the dogs as individuals are very well trained.

My sister's and parents' dogs have never met my mother-in-law's dog. My mother-in-law's dog is not well socialized and she is poorly behaved as well as a nervous wreck. We had her over once (just mother-in-law and her dog) and it was a disaster. She had several accidents and was yelping, whining, and shaking. When we visit her, the dog has to be in a different room than the kids because she gets either overexcited and knocks them over constantly or she gets freaked out and has a panic attack. Her dog is two and she has never done socialization classes or obedience training. The dog is a mess.

My mother-in-law says that it isn't fair that my family gets to bring their dogs and she doesn't get to bring hers. My husband told her that if her dog was well-behaved and predictable/friendly with other dogs, people and kids, we'd be happy to have her but the dog is not. My mother-in-law told us that we don't give her dog a chance because she's not welcome in our house.

My husband explained to her that my sister's dog is essentially medical equipment and my parents aren't going to put their dog in a kennel for three or four days, especially when she's well behaved. We also explained that this was not a planned event, it was just a casual invite.

She still says it's unfair and she feels like we're discriminating against her dog. My husband told her if that's how she feels fine, but the answer is still no. We have to watch out for everyone's best interests and especially my sister's dog. While the dog isn't technically "working" when she visits since we all can assist with a seizure, we can't afford to have my mother-in-law's dog getting reactive and hurting the Aussie.

My mother-in-law told us that if we want to keep things fair, we can't have a "no dog rule" at our house but allow these two dogs and no other dogs. My husband and I said we can do whatever we like in our home, thank you.

Are we being unfair, or is what we're doing completely reasonable given the circumstances?