An update on this: no, I didn’t end up applying for the GNOME Women’s Summer Outreach Program.
While in a way I’m relieved that I don’t have to do it during my busy upcoming conferences and diving trip, I had a rather disappointing experience trying to apply where it turned out that the potential project listed on the wiki did not have a mentor who knew anything about it or believed it would work, and I couldn’t find any related projects due to everyone of interest going to GUADEC 2006 and simply stopping using their email. I did try and organise it in the last week, but not actually at the last minute, so although I could have been better too, that wasn’t very pleasing.
I will consider more seriously applying directly to Summer of Code, assuming it runs again, next year, although not necessarily on GNOME projects. It will depend on what I feel is of interest at the time.