Phi Mu's Pledging ceremony requires that all members wear pastel, with white or off-white being the preferred color. I think that's pretty much because there are usually only a few days between when girls are given bids and when Pledging is held, so it's easier for them to find
something to wear that's pastel. Initiation, however, requires white or off-white, even if it's only a slip (does anyone actually
wear slips anymore outside of Ritual?).
One of my favorite stores is
White House | Black Market, and they usually have some white dresses (and SKIRTS! Don't forget that is usually an option, too!) available.
This one is my personal favorite of their current styles, but they also have a few nice ones on clearance, too. (
Here,
here,
here, and
here.) And, I can tell you from experience, their clothing almost always fits and flatters me, and I'm a bit of a teapot--a short and stout size 12. Hope you find something cute!
And, as a side note... I seem to remember being taught growing up that, if you can't say something nice, you shouldn't say anything at all. Seems we all need a little reminder of that once in a while.