two insurances at once and gender affirming care?

i am currently in the process of getting a gender affirming surgery that had been determined as a medical necessity, though my insurance does not cover gender affirming care. i will either have to self-pay, though i am unsure if i will have enough money saved by the time of the appointment, or i need to find a new insurance provider. i am 19 and have no knowledge on this topic so i could really use some help. 1. i am currently on my mom's plan but i am still looking into insurance for this year, despite enrollment being closed. i see now harm in checking if my situation will make me eligible so i plan to. the issue is: i may end up having two insurances at once and i am not sure how to manage that or if that's even legal? it may not be possible for me to leave my mom's insurance immediately. 2. is there any specific company that anyone can recommend for me, who is specifically seeking coverage for gender affirming care?