Unless MD law is very different from that of other states, it depends upon your insurance plan.
If your insurance is under a Section 125 plan, you can only make changes during your yearly open enrollment period or when you have a qualifying event. This is Federal law. A divorce would be a qualifying event, but you would have to wait until the divorce is finalized. If your portion of the premium is being taken out of your paycheck pre-tax, or if you have the option of taking it pre-tax, then you are under a Section 125 plan.
If you are not under a Section 125 plan, then it's up to the insurance contract when they will permit you to make changes. However, the very large majority of plans require that you wait for open enrollment or a qualifying event, which again would mean waiting till the divorce is final. If your portion of the premium is deducted from your paycheck post-tax and there is no option to take it pre-tax, then the likelihood is that you are not under a Section 125 plan.
If your employer pays 100% of the premium, you will have to ask someone in your HR department whether or not you are in a Section 125 or not. Regardless of the answer, it is very unlikely that you will be able to drop her before the divorce is final, unless you have an open enrollment period before then.
Regardless of when and how she is dropped from the plan, at that time your company will provide her with the information as to how she can continue the coverage at her own expense. This is also Federal law and NOTHING you do can prevent that from happening.