Over the years she did vary the way she signed her name, the 1929 signature is so sad, but even than she used a forward slant. Sometimes, she started her capitals at the top, others times at the bottom; her lower case letters stay pretty consistent, look at her “d” & “y.” I went through some of the signatures of Mabel that I had on my computer but I know that somewhere there are others on photos and in books in my collection but these example are pretty indicative of her style.
Marilyn
"Looking-for-Mabel"