I am not at keen on Martha - she is such a dreary drudge in the Bible
But in MN-land, doesn't that conversely mean that Mary would be considered a Disney Mum? 
I love the name Martha, but IMHO, Lily has become a bit too ubiquitous of late. I know it's a middle name and not a double-barrelled first name, but I still think that, on the occasions when all the names are said, the two names next to each other sound a bit too frivolous and sing-songy. I'd personally go for a one or three-syllable (with emphasis on the middle syllable e.g. Rebecca) name to contrast nicely with and define Martha in a pleasant-sounding way. And I'd say not one starting with a vowel - it's one of my pet hates when two names together invite a horrible fake 'R' in between, e.g. Selena RAlice or Lisa RAnderson.