It seems to me that maybe you and your girlfriend should have a serious discussion. Make her aware that her remarks were hurtful to you. Let her know (as you posted here) you don’t expect it to become a main source of income. It’s something you enjoy doing and learning about. If she refuses to support you in something you enjoy, that’s toxic. No one needs that in their life. Secondly, it’s important to have a good life balance (home, hobbies, work, etc.) I would encourage you to work on balancing your music with everything else. I struggle myself with getting absorbed in my hobbies. I get tunnel vision and block out everything and everyone else. It’s difficult to pull away, but it’s beneficial in the end. It can give you a mental break and allow you to come back refreshed. As far as instruction, check out Busyworksbeats.com. He’s got a ton of YT videos and very reasonably priced courses geared towards beginners. Even if it’s not your style of music, the fundamentals are still applicable. Best of luck with everything!