Do I tell my mother about my girlfriend?

My mother, and the rest of my family, already know that I'm gay. They've never had a problem with it, especially my mother.

However, one thing does worry me. About two months ago, I developed a crush on a girl I speak with online. After I told her, she said that she feels the same, and we began calling each other our girlfriends.

I'm worried about whether or not I should tell my mom. I always want her to know that I'm honest with her and that I can be trusted with using the internet, so I don't want to lie and keep calling this girl just my friend, but I'm worried about how she'll react to me having a romantic relationship with someone I've never met in real life. I doubt she'll forbid me from talking to her or anything like that, since she's usually very calm and reasonable, but she might get worried.

I talked to a close friend of mine about it, and he said that he personally wouldn't tell his parents, since it'd just cause drama and worry. I agreed with him, but... the difference between he and I is that he's eighteen. He doesn't have to tell his parents if he doesn't want to, because he takes care of himself. I'm fifteen, still in my mother's care, so I feel like maybe I should tell her. Just calling this girl my friend instead of my girlfriend feels like lying.

What do you guys think I should do?

 

Thanks, Boudicca. I'm gonna give it just a little more thought, but I think I will end up telling her.