Good advices but things went wrong quite fast.
Yesterday, on my way home, i noticed she and her boyfriend were arguing so i told myself : Alright, i won't be a part of it, I'll just walk by and pretend I'm not seeing anything.
However, when i got close to them the guy yelled "Hey, look, it's your boyfriend" while squeezing her wrists.
She started crying and told him "Stop, you're hurting me!"
I couldn't just let this happen so, i tried to reason with him by claiming i wasn't interested in her and he had nothing to worry about.
Unfortunately, he didn't believe my lie and became violent. At this point i knew an ass kicking was inevitable.
He tried to punch me, i got lucky and blocked his punch, twisted his arm behind his back, grabbed his leg with my other arm, he face planned into the ground and i pinned him down.
Some stranger walking by came to my rescue after i explained what had happened cause i was obviously having trouble keeping him down.
Long story short, we had to spend the night at the police station explaining what had happened, she decided to press charges against him, thanked me with a big bear hug and the guy is temporarily in jail until things get sorted out.
Everything worked out for everybody in the end.
I'm now her hero and the guy is behind bars until we go to court and testify against him.