My mom usually catches on to things pretty easily. I don't think I've been too obvious about also liking girls, most people just think I'm a straight ally, although I do own a couple rainbow bracelets and I go to our school's GSA club sometimes. A few weeks ago I was slightly sick and had a small cough, and my mom said "No offense, but at school maybe try not to clear your throat as much because if there's a cute guy or girl nearby it sounds kinda gross." Which was a bit surprising but the or girl part was what got me. Then today we started talking about things, and somewhere in there she asked "And what about you? Do you have a guy or girl crush?" I said no, because I don't like talking to parents about that, but yeah I do, one or two guys and a girl. So I'm pretty sure she knows but I don't really feel any need to tell her yet. And the other day the girl I like randomly came up to me and started talking about freezing morning band camp and how she accidentally banged her face against the french horn, it was kinda awesome.
It sounds like she does suspect something, although she doesn't seem massively troubled with it right now given her light tone. I don't know your mum, but perhaps it could be that she's just really open minded? I saw a post from another user here whose dad would ask him if he liked girls or guys just because he was an unassuming dad, so...
Even if she doesn't know, which she probably does, at least it sounds like she's completely open and OK with it. That's got to be a good place to start from
Either she is so open-minded she is beating you to the conclusion, or she suspects something and treats your orientation as a complete non-issue. Which is what I hope it becomes for everybody in time. Tell her you're open to girls when ready.
