Is there a law in uae if my friend is cheating on...

We would like to inform you that if your boyfriend cheating you and meets your friend in particular, then that act is not punished in the UAE Penal Code
But if there is an outrageous act that violates modesty or comes up with any statement or action that would violate public morals, then the penalty for that matter is imprisonment for a period of no less than six months.

This is according to the provisions of the Penal Code, which states: -
Article 358
Whoever publicly commits an indecent act shall be punished by imprisonment for a period of no less than six months.
The same penalty shall be imposed on anyone who comes to say or do anything that violates public morals.
Whoever commits an indecent act with a female or boy under fifteen years of age, even if not in public, shall be imprisoned for a period of no less than a year.