Does a will become invalid if the residence changes states?

No, the will is valid if it was properly executed in the State it originated from. However, you may want to consult an attorney anyway b/c some of your assumptions may be incorrect. For example, Florida has a unique homestead law. There may also be differences in exempt property, executor requirements, etc. Advance directives such as living wills, durable powers of attorney and health surrogates may also be different.

While recommended, it may not be necessarily required. The question is whether a Maryland Will complies with Florida law once the Testator/Testatrix becomes a Florida resident. Florida basically requires 2 witnesses and that the Will is signed at the end in front of everyone who signs the Will. If it does, it can be valid. If not, it won't. The Will does not have to be changed just because your daughter changed her name. But if you update your Will, it should be updated as well.