Dear Confused in Maryland:
Who says she has to move in with you? You could set up separate living arrangements in Maryland. That way if things don't work out it will be easier for her to move back to Tennessee. If things do work out she can move in. This doesn't have to be an all-or-nothing proposition.
Just remember, unless you make a lifelong commitment you don't have to spend the rest of your life with her even if she does move in with you. You're not stuck for life so don't think of it as the worst thing you will have done.
Who says she has to move in with you? You could set up separate living arrangements in Maryland. That way if things don't work out it will be easier for her to move back to Tennessee. If things do work out she can move in. This doesn't have to be an all-or-nothing proposition.
Just remember, unless you make a lifelong commitment you don't have to spend the rest of your life with her even if she does move in with you. You're not stuck for life so don't think of it as the worst thing you will have done.