That isn't a reason. You're the one who's being childish if you're upset at the FANDOM she participates in. I'm 24 and MLP is one of my favorite things. If you hate me for that, I don't care because I'm a fucking adult and could care less about a petulant child's opinion of me. I have a husband and daughter, too. Just because you like a FAMILY show that doesn't mean you're immature/incapable of being an adult. In fact the show has many messages you could benefit from. Like not being a bully. And FYI, this fandom has a lot of people willing to buy commissions, and that helps me afford things outside of the internet. In fact, it's saved me from not being able to pay rent. Without this fandom I would probably be homeless because of our current situation, and it's getting better.
You've got a lot to learn, kiddo. Get off the internet and grow up a few pegs.