Girl at the gym

Im sure people will insult me and call me a pervert here. But its a genuine question if what I did was reasonable or if I should feel bad.

There is an attractive girl at the gym that obviously checks me out. She said shes "almost 17". She always tries to spark a conversation with me. Shes one of those very outgoing personalities. But here's the thing, she basically asked me if we could go hangout and drink. My response was "we will see when you turn 18". Later on I thought about it and thought maybe that was abit wrong to say. Im in my 30s and its not everyday a very attractive girl comes onto me like this. Am I being too impulsive by saying "when ur 18"? Is this creeper behavior