I totally understand.How old are you?
I recently had a sliding genio and planned on not telling my family (I had some saving from a student job).But Then I met surgeon who told me I would get covered by my insurance (I'm in Europe), and it made things a lot easier, so I finally figured out I would be better off telling my family, even though I knew I would face some opposition.
I faced some very negative reactions, but I stood my ground, saying that it didn't matter if they didn't support me, I would get it still, and go on my own to the clinic.Facing my determination, my mom especially, had no choice but to accept, and finally stand by me during the process.
I'm planning on getting jaw surgery as well, since I just figured out I had sleep apnea, and , once again, I know they won't approve, telling me I'm insane...But anyway,if I want to, I will get it done, not matter what.
So, here's my advice :
-Get a sleep study done, it might "justify" your jaw surgery and help for insurance to cover it.If you try hard enough, you will certainly find a way to get it covered, sleep study is kind of straightforward.If it doesn't work, go see a maxfax surgeon, discuss financing, you may find a way to get it covered.
-Tell your mom, and repeat it as often as necessary,even if she doesn't want to hear eventually, she will get used to it, don't try to hide it, open up.Take a deep breathe, and tell her, show her you made up your mind.Even if she still doesn't support you down the line, you're a grown up, and if you decided to go for it alone, at least, they will know.If she sees your determination, she won't let you go to the hospital on your own, she will want to stand by you.
Don't talk aesthetics to your mom, talk functional, say you have trouble breathing , swallowing, sleeping...A weak jaw is not only about looks,it definitely has some functional consequences.
-And last, but not least, make up your mind.It's an invasive surgery you're planning on having, you need to be mentally strong.It involves some risks you need to be aware of. I know how obsessing it can get,but be aware that even after your surgery, it won't be "perfect" and if you're over conscious now, it might even get worse afterwards. Once again, breathe, relax, jaw surgery takes times, it's definitively a process. In the meantime, live your life, obsessing and getting depressed is not good before any surgery.
Try to see things as a whole,negative mindset, fear and worry will only get you worse, and won't help you to archive your goals.
Best regards