I'm going to make my girlfriend have a mental breakdown.
Why would you want your girlfriend to have a breakdown?
To make it easier to control her.
Causing your girlfriend to have a mental breakdown is a sick idea. It could permanently damage her mental health.
I love her and I don't want her to leave me. I just want to fix her mood swings.
Trying to control her by having a mental breakdown is no way to fix her mood swings. If she's having issues, perhaps suggest she see a therapist?