That would totally depend on her age. If she's 14 and he's 20, that's a no no. If she's 22 and he's 28, that's fine.
I have a friend and she has a crush on the guy that's 6 years older then her. She keeps on asking me if it's okay to like a older guy but I never know what to say! Help!
It's totally fine to "like" or have a "crush" on someone that is older. The problem comes when she wants to have a boyfriend and she is underage.
Should sex enter the picture at any time while she is a minor, and he is majority age, he could get charged with rape, he could have to register as a sex offender and her mom and dad would probably keep her locked in the basement until she graduated from high school. OK - maybe not that last part.
If she is still in school, she should date boys her own age. If she deems them too immature, have her wait until she graduates from high school. By then, it won't be a problem.
It honestly depends on her age.