I would think pre emptive prison would be the last route... I wasn't offered bail, ankle bracelet, etc.
You're at flight risk, accused of violence against women. The judge made the right decision within the circumstances he was presented with at the moment of the arraignment. No one wants to be THAT one who easily set free someone who ended up either fleeing the country or harming the victim, as this has happened before.
Locals get preventiva all the time for stuff like this, but it seems you expected some sort of special treatment just for being a U.S. citizen.
Arraingments are not about being guilty, and the person doesn't need to be held for three months. Some People get bail with a "revision". The problem might be that you dont have "arraigo" in the D.R. , no businesses, no other relatives?, no home, apart from the place you shared with your gf. Is that correct?
It doesn't matter if your gf changed ther mind, as she has already set the case in motion and it's a matter of "public action"now. Also many women are coerced into dropping the cases, so they're careful with that.
As Long as the prosecution has some evidence, they can push the case.
Also if the prosecutor runs out of evidence to sutain a trial, they will drop it. Unfortunately, sometimes they wait the three full months or ask for 3 more months to investigate more.
A good lawyer can help you. You dont need to para anyone.
Watch out with people who approach you asking you for money saying it's to pay the judge. This is for themselves!