Some of my best guests have been 18 to 25, @Ayanna2, but some other hosts' bad guests have been that age. Very bad. Property destruction. If you are having trouble booking, and I see you have no reviews yet, make your initial message to the host wonderful. Tell her what it is you love about her place, mention anything in her rules that is maybe a little different and tell her you will absolutely do that thing (take your shoes off, or keep the quiet hours or whatever), assure her you are responsible, give examples. When she accepts, be the absolute best guest ever. Then you will get a five-star review and it will be no problem booking with any future host.
I'm sorry you have to go the extra mile on this because of your age, but it's worth it!