I'm going to defend my ex girlfriend in front of my current girlfriend
Why do you feel a need to defend your ex?
No, I'm just trying to keep my relationship with my ex girlfriend still in good terms
I can see the predicament that you are in. It is expected to be loyal to your current partner. I know you want things to be good with your ex but you shouldn't make your current partner upset.
It's not like I can't convince my girlfriend that I'm not flirting with my ex since we had a fight about it.
By defending your ex in front of your girlfriend, you may be disrespecting your current partner. It's best to consider how your girlfriend feels first so that you do not destroy your relationship.