Hopefully in time she will be more supportive, it's difficult for some to accept when views are so ingrained.
I'm a guy and never took a girl home from school to somewhere around 20-21 years old or so. I soon heard via my brother's girlfriend that my father's first words after this were along the lines of, "well at least we know now he's not gay".
Actually, I'm bisexual, and that of course is why my parents do not know. Too many of older generations are not going to change.
Many of my closer friends over the years know of my sexuality, including my current partner and last few. In a work trip with a female colleague we were talking and I told her, her first words were, "how do you know?" due to only ever seeing me with female partners (I have three children with two different women). I asked her how she knows she's attracted to guys...
Anyhow, every single person of my age and below (I'm 37) has been totally accepting from the moment I've said anything, so I think it's just a case of the ages.
I'm guessing your mom still hasn't met any partners? That might help to convince her it's not a phase or something that needs to be corrected.
Stay proud of who you are, you don't need to change anything