I can't even imagine what that poor dog went through in his final moments. The fact that she tried to make sure the neighbors wouldn't hear his screams shows that she knew the pain she was going to put him through, and having the person he love and trusted most in the world...his MOTHER...essentially torture him to death...
There are no curses in Elvish, Entish or the tongues of Man for this treachery.
I sincerely hope this woman loses her rat to someone who will take good care of it and that she's banned from ever owning any animal again. At least when I realized I wasn't capable of giving my ferret the love and attention she deserved, I found her another home.