My Mom Continues to Dismiss My Relationship [M22], and It's Impacting My Girlfriend [F20] — Any Advice?

I've been in a relationship with my girlfriend for a while now. We met on an app around mid to late September, started taking an interest in each other in mid to late October, and officially became a couple a week ago. I've been transparent with my parents about our relationship since we first connected. My dad occasionally asks about her and seems fine with it, but my mom tends to dismiss the topic whenever I bring her up, even from the start, despite not having met her yet. It's clear she has reservations about my girlfriend, even if she doesn't openly express them. I've shared my mom's feelings with my girlfriend and have been honest about the situation, but I don't think she fully grasps why my mom is acting this way, and honestly, I'm a bit perplexed as well. From my perspective, I feel like the natural next step would be for my parents—especially my mom—to at least recognize my girlfriend and eventually meet her so they can get to know each other. One parent is receptive while the other isn't. Given my mom's strong opinions, I doubt her feelings will change as she tends to be quite stubborn and holds onto her beliefs. I've tried discussing it with my mom before, but I'm not pushing the issue at this point. I want to avoid creating any unnecessary tension. My girlfriend remains my partner, but we've had our ups and downs, leaving me feeling somewhat stuck. What are your thoughts?