What should I do to protect myself from false criminal charges?

I'm going through a divorce and custody matter with my two year old daughter. My husband's female friend obtained a protective order on me stating I sent her violent threatening text messages, trespassed on her property, stole her vehicle and set it on fire which was recovered a block away from my husbands home. I live and work in VA. No one from the state of MD contacted me, no police, investigators or anything. Only her insurance company who I was fully cooperative with and informed them I would provide whatever they needed because I did not do the things I was accused of. I did speak with the State Attorney office, and I all I was told was I can expunge the information which was only dropped due to a Nolle Prosequi? This is permanent regardless of an expungement. And because of MD law I need to know how I can protect myself against this person who also will be a witness probably for my spouse being that this is one of his friends? She can keep making false statements against me at anytime through the state of MD. In an attempt to help my spouse, what can I do?