I can't help with advice for parking in Baltimore, sorry!
However, unless you're going on an Acela, I'd find a Regional train that stops at Aberdeen, MD which would be much closer to Northeast, MD (the town). I'd guess at least 20 miles or more closer to her. This would save her time, gas, and the frustration of driving into center city Baltimore. Alternatively, you could get off in Newark, Del, which is also closer to Northeast albeit in the other direction from Aberdeen.
Finally, another alternative and one that is viable if you are on Acela, is to get off in Baltimore. Then catch a northbound MARC train (Maryland's commuter rail system) to Perryville, MD. Perryville is just down the road from Northeast, maybe 8 miles away.