Here in the Pacific Northwest it's definitely "mor-EEN." (I'd use an upside down "e" but I don't know how.)
My niece has apparently inspired other little Maureens in her town. Three have been enrolled at a nearby school since she went through in the 1990s. Her mother (my SIL) is a teacher so she's up on these things.
Anyway. This is a long winded way of saying that here in Seattle / Spokane, it's pronounced with the stress on the second syllable. I prefer it on the first. But there it is.