Don't worry or give up! Many of the top level women cyclists in this country are in their 30's or older.

I started riding competitively this year and I'm 34. Many of my team mates are older than I am (who can kick my butt by the way). Just remember that even if you are already fit, it takes time to "get your legs", some people say about 2 years and that sometimes knowing racing tactics is more important than merely being strong. Keep riding and you'll be smoking the 25 y/o's.