Shawn,
Your clause is not enforceable and your tenant has not yet abandoned the unit. If she said she will be out in two weeks, set up a time to meet her at that time and get a "Release to the Rights of Possession Form" signed (see my files). That will give you possession of the property and you can move forward even if she leaves stuff.
In the meantime, you can file for eviction if she has not paid you. Be sure your lease has the "waiver of notice" clause. If not you have to send notice to pay or quit before you file or your case will be thrown out.
If you never hear from her again, you can then assume she has abandoned the place. That process will take at least 30 to 60 days to complete before you get possession. In other words, a long time and then you have to store the stuff.
Eviction is expensive and cumbersome and abandonment takes time. Can you offer her some cash ($100?) to sign the above mentioned release form (read up on cash for keys)? Trust me, it will be easier and cheaper. If you decide to go the eviction route, use an attorney experienced in that process in this area. Do not try to do it from MD.
Good luck from a former Marylander,
Kevin