I have an ault charge Texas, both the victim and I stated that I was not guilty but there is a witness?

My girlfriend and I got into an argument outside of our apartments wherein yelling ensued, finally waking neighbors. Then she got angry and started running down the street and I went after her trying to grab onto her to get her to stop from running and we both fell into the gr. After this, a lady came out yelling at me that she had called the cops, and sure enough, they arrive, and now I am being charged with a cl c ault(texas). My girlfriend knows I am not guilty and so do I, but what about the "witness"? I have yet to go to trial, and I am worried that I will be charged as guilty and my girlfriend be charged for lying because someone claims to have seen me hit(I'm not sure what the allegations are exactly, but some form of ault apparently) her. I've a clean record so the maximum sentence is $500, but I've heard that for domestic violence, the misdemeanor can be bumped up to a felony. Now what just might happen?