I had to do many iterations through clues 4, 7, 9, 11, and 12 to arrive at a point where everything fell into place.
I think the reason this puzzle is difficult is because so many passes through the of/either (XOR) type of clue are needed.
When I solved this puzzle, the first pass didn't lead to any positives, and there was a lot of white space.
Several passes through the of/either clues mentioned above, led to a resolution for clues 11 and 12. Onawa = 12.5 and Audrey = 1952.
After transposing these two positives, there was still a lot of white space.
Several iterations through clues 3, 4, 7, 8, and 9 finally resulted in Granger could not be 16.9. Before this exclusion, 16.9 could only be Granger and Zamora. Excluding Granger meant that 16.9 = Zamora.
Then clue 9 gave 1964 = Mabel.
From there, everything fell into place. If I did this right, the solution is:
1944 - Wilma - 12.5 - Onawa
1948 - Kristy - 15.7 - Velma
1952 - Audrey - 13.1 - Tomales
1956 - Pam - 16.9 - Zamora
1960 - Velma - 17.4 - Rockford
1964 - Mabel - 18.5 - Granger
The new hint system is awesome. It has a special message for those rare occasions when it can't come up with the words to explain the next step. There is at least one puzzle in the 4x7 library that will delight you with that message if you ask for a hint at the right time.