You’re kind of going off on her saying he grabbed her arm. It’s clear you take it to mean that he manhandled her. And you’re excoriating her for letting him be abusive toward her.

I’ve worked in a restraunt too. People grabbed my arm all the time to get my attention. It wasn’t manhandling. It’s a gentle hold. Customers do it to get my attention, usually when they’re mouths are full and they want to ask for something while I’m nearby. Managers and co-workers do it to point something out quietly or to ask for help, etc. And yes, boyfriends have done it at my place of work, to quietly let me know they are there, etc.

Use of the phrase 'grabbed my arm' is not inherently violent. It depends on the context.

I did not get a violent context out of this use. She was at work and he 'grabbed her arm' in the manner of he 'pulled her aside' to request a different seat. The problem there was the exhibit of bias, not that he touched her.