no, this is not realistic. It could easily take her 75+ minutes in the morning. Going home, I would imagine even longer. This could be theoretically possible, imho, if she was working from, say, 11 am to 7 pm or 8pm. Or doing this commute once or twice a week. but daily? no.
Our nanny commutes from Germantown to North Bethesda. She has come at different times over the years. The commute takes her a LONG time (I think usually 1 hour plus) and is unpredictable because there are so often huge tieups.