I'm going to catfish my girlfriend to see if she is loyal
Why do you want to do that?
I suspect she has not been loyal to me
She's your partner so you should trust her. It's not ok to trick her by catfishing her.
What do you know? I've been catfishing her for months.
Relationships are hard but they are even harder if there is no trust. It will cause fights and arguments and the relationship will suffer. It is better to be honest and seek counseling if you want the relationship to work out.