Notice how they seem to be focused on the pool set, calling it a "hot tub" when in fact it's a Splash Pool. They conveniently omit the Inventor's Workshop, or others which were released publicly at the same time.
The LEGO Group's 1981 advertisement SPARKsummit uses in its campaign is merely one ad featuring girls TLG has put forth over the decades.
In that advertisement the word "beautiful" is actually there as a description of the creation the girl built -- that it wasn't necessarily a "set" nor did it have uniform colors like sets it is still beautiful.
Link to article: http://blog.sfgate.com/mmagowan/2011/12/21/new-legos-for-girls-get-triple-s-for-sterotyping/
Just because there are no pink bricks visible in the 1981 ad isn't because LEGO didn't make pink bricks at the time; the very creation itself as being "beautiful" is to which the ad is referring. The very act of any gender using LEGO bricks in a spatially-imagined creation is beautiful in the eyes of the beholder.