I noticed the same thing when leveling up. Seems the game starts with a complete new gene pool with each level (fugly and frigid). I cheated a bit with the new girls by using the SMA Editor online. I replaced the appearance of a few in each days group and tweaked the personalities so I knew I would get at least a couple which would get good ratings.Got the girls up in like week 3-4 to being kinda sleezy.
Nearly every one was workable in some way to sex.
And then I hit lvl 2 and was able to add another base girl profile.
Which somehow reset all my girls to being like week one frigid.
Tried taking out second profile leaving the first, but no go, its like starting all over again.
Here is a couple examples of current girls who are at levels 0 and 1 (user level 4).