I really want a lip piercing but mum said they look horrible?

i really like the look of a lip piercing and i'd like to get one. I've found a tattoo shop in my area that does them and its �30 which i'd be able to afford. When i asked my mum she said they look horrible and i can't get one. Its my body and i really want one. I'm 15 and when i turn 16 i can get it done without my parents consent, which i wouldn't like to do because its like i'm going against them. I haven't told my dad but when i wanted my ears pierced my mum was going to make me wait till i turned 14, but my dad convinced her to let me get it done when i was 10. How can i convince them to let me get one?