I have a theory about Freddy's mother.
Her name was Emma hunter and she was a weredog along with her parents. She worked at an animal centre and was even vegetarian. However unlike her doggy friends, Emma wasn't scared of the wolves and even found them fascinating. then one day, the animal centre caught fire and the wolves came to help.
That's when Emma met flash-heart and hotspur
After meeting her in both their human and wolf/dog forms, both of the lupin brothers fell in love with her, but In the end she chose flash-heart
Her cause of death was childbirth