Roommate & her evil dogs

My roommate got another dog after I told her not to. The introduction of the new dog made her other dog territorial and she attacked and wounded my dog for the first time over the weekend which led to a trip to the vet. I tried discussing this with her to come up with a resolution but she got defensive and it turned into a screaming match with the wrongful inclusion of her boyfriend. They were incredibly rude and showed no remorse or concern for my dog getting hurt and I am filled with rage.

How should I get back at them, legally and without hurting anyone? I was thinking about handling this like a reasonable person, but I'm extremely upset about my dog getting hurt and I never intend on being cordial with this person ever again.