YOU SAID:

she can't be what you need if she's 17

INTO JAPANESE

彼女が17歳なら、あなたが必要とするものにはなれない

BACK INTO ENGLISH

If she's 17, she can't be what you need.

INTO JAPANESE

彼女が17歳なら、彼女はあなたが必要とするものになることはできません。

BACK INTO ENGLISH

If she's 17, she can't be what you need.