A 17 year old girl likes me that way I’m 27 , what should I say to her ?

I would think that, unless you wish to stay out of prison, you'll say no to her for a little longer.

I understand what "that way" means it means she likes you as a boyfriend but others might not understand 

say hi to underage sex...............

There is an age gap of 10 years . Tell her you can treat me like an elder brother . Right now concentrate on your studies . When you are over 18 think about starting an affair . I am sure you will get a boy much younger than me to be in love . 

Tell her you're not interested in little girls, but she can try again when she's 21. 

Grown men shouldn’t deal with teenage girls.

"Good-bye" probably! Depending on the laws where you live.

Give her a few years.  You don't want to be accused of hosing out a minor.

tell her shes a minor and i aint going to jail

Tell her to wait a year.