u have two options
either run away with ur gal or forget her......u have to choose the best for you...........
if u run ...do arya samaj mandir marriage..... register in court ....live happily but without your parent's blessings.....alos note you would also be protected by local police....(not all the time)
think twice before u take any final decision..... it may hurt u in future...choice is urs....
now genuine advice : try to convince atleast ur parents, or ur gal's parents atleast....either of the parent's support is must.....in marriages like this.....u and ur gal would be on safer side for future.....lastly i dont think u have become that much mature to take responsibility (of wife/family) as yet....dont mind but i am saying coz u have just crossed ur teens age and u are just 21 ....!! take some more time.......
rest upon u both....
All the Best....