Landlord threatening to kick me out due to guest being there when I wasn’t

I’ve been at this apartment for less than 2 weeks, and I pointed out some things to my property manager that needed fixing around the apartment. The fix was scheduled at a time when I was at work, but my girlfriend, who is not on the lease, had spent the night before. I told my girlfriend that she needs to be out before they come, basically just getting ready in the morning and leaving, but they came early, and they’re now saying I violated my lease by having guests over while I wasn’t home. This seems like a bit of an overreaction to me, as it wasn’t as if it was 5PM and I was gone and she was just there, she simply hadn’t awoken yet. Does this seem like something they could even do? Or are they just trying to make an example out of me?