Indeed. I have asked numerous times before about the 'striped shirt' version, and interestingly enough, quite a few people do recall it. I believe one woman who worked something with audio editing recalled that version, and a few British fans of the film remember seeing it on television as well. I began to lose hope after finding little to no information about it. But then after learning that the brunette extra could be Joyce Gibson, it rekindled hope since as I had stated before, I'm pretty sure she's the girl in the striped shirt version. Nonetheless, I find it odd that there would be two versions of what is essentially the same joke. Still, I want to find it.
Awhile back, on the Airplane! wikipedia page, some trivia had been included stating that there were indeed two versions. The striped shirt version replaced the gelatin version on television because supposedly the woman's white shirt had the words Moral Majority printed on it. Apparently, later versions had the Moral Majority writing digitally removed. Sounds a little far fetched to me, but it would explain why two versions were made. Well, assuming that little bit of trivia is accurate.