I don't know your entire situation obviously but here is my two cents!
It's not always just about social stigma (unless she said it was, but even so, haha) - family members worry about safety, your future opportunities, the long-term outcomes of what might seem fun when you're 20 but might negatively affect you when you're 40. It doesn't mean these are necessarily right, or fair, or things you can't worry about for yourself -- but I think most family members and friends do come from a place of caring about you, and in my case, it helped me to remember that. Sometimes the first reaction when a girl posts something like this is "fuck them if they don't want you to be happy" but I think it's more complicated than that. I worry about my friend who plays football, even though he loves it, and I think it's equally fair to my friends to worry about me, even if I love it. Especially because they don't necessarily understand the reasons why you love it.
But beyond that - you are an adult, and unless your family is able and willing to foot all of your bills/savings/fun money (and you want them to) - you need to take care of yourself, and you get to decide what you do. I had to simply stop talking about work and refuse to discuss it with someone who wanted me to stop. Your mom doesn't have authority over Adult-You and if this is what makes you happy, or what you need to do to get by, or what you want to do now even if you decide later you don't want to - that's your choice. Saying "I understand you don't approve, and I appreciate that you love me and worry, but this is my choice and you don't have to love it, but you do need to respect it" might not get you a super desirable response but I think standing up for your choice while also making it clear that you don't *need* her support to do it can be effective. I personally found that being super defensive didn't really help but eventually saying "this is my choice, we don't have to hash it out, I love you and I want to drop it" did for me.
Either way, big hug. It's such a crummy situation to be in. I hope things work out well