Staying in an abusive relationship is part of the dynamic of being a victim of domestic abuse. Sure, there are cases where it was just an argument that got out of hand or both parties had a little too much to drink without it necessarily being a pattern of abuse or alcoholism (that was certainly Brett Myers' story according to him). But just as often as not the victim may want to leave but can't, for emotional reasons, for economic reasons, because of kids, all kinds of things.
In Herrera's case, let's not forget, his girlfriend is 20, she's not an American citizen, and she (like him) is from what might currently be the most impoverished and violence-plagued country in the hemisphere. I'd probably stay in the relationship with my millionaire boyfriend who lives in the US too (and I don't say that to impugn her in any way).
Note, also, that when the case was adjudicated, she had to give a statement saying she was not coerced or pressured to not testify in any way. And I will assume that's true. But it's all too common, and actually part of the abuse, i.e. they fear for their safety if they testify, especially if their abuser is not convicted or doesn't do much time. Sometimes nothing has to be said, even (just like with the mob).
I sincerely hope none of this is the case with Herrera, that he made a mistake, that he's contrite, and that when he completes his suspension and counseling he comes out of it a better person...and a better player. Truth is this might save his career, not ruin it, because it was already spiraling for baseball reasons, and he was already a player with focus/emotional control issues. The only reason the Phillies can release him is for baseball reasons, so if he's not traded he might absolutely get the chance to make the team next spring. But will he actually be one the 5 best OFs? Not clear at all (especially if they acquire one this month or in the off-season).
I'm sure if the Phillies do keep him there will be a lot of public contrition, especially since Kapler is already involved in that area (despite his own questionable incidents with LA). Donations to domestic violence groups, an awareness campaign, etc.