5 month old female has started growling at her brother?

[donnad]

Hi, Just my 2 cents worth. When I had Miss Ginger spayed at 5 months, she was just starting her first heat cycle. I know Neevie had some issues, although thank God Ginger got through her surgery just fine. So maybe she is coming of age. I had no clue except when I was rubbing her belly, it felt like she had little tiny marbles under her skin hahaha