I need to know, was I gaslighting?

My roommates dog bit my baby. Full story is a week ago, it was dark in the living room and my child ran out like he usually does when we go out there, my roommate's dog was apparently laying down, no one really saw what happened, my wife was only a few feet away and all of a sudden we hear barking grumbling and the dog was on top of our child and he was bitten. Ever since that happened my child is very scared of that dog. My roommate made assumptions that my child stepped on him, but we really don't know exactly what happened, it could be that my child bumped into him, but the dog is a little too big to step on unless it was his tail. My child is really scared of the dog and cries when the dog comes closer and Everytime my roommates sees that she says "Well don't step on the dog if you don't want to get bitten" "stop crying when you see the dog" "he needs to get over it"
So I finally said "we have no idea what happened" and "dogs shouldn't bite or become aggressive to any child" and she turns around and gives me a angry glare and asked "are you gaslighting me?" And I replied, "no I'm not gaslighting you, no one actually saw what happened" and followed" you were asleep when it happened so you can't say that my 3 year old child was the cause of this. And she continued to be pissed at me. Plus the dog has bitten me before and snapped and almost nipped my wife ehen she tried to put the dog in another room because someone was at the door and the dog kept barking. Anyways we didn't see what happened and my roommate was asleep when it happened so theres nothing we can do, but I hate it when people make assumptions. I kept trying to think how I gaslighted her because that's what she told me I was doing and I don't get it