She's now pulling herself up all the time with no troubles. Until tonight, even though she is able to plop herself down, most of the time she'll whimper or cry until I realize that she wants me to help her. This evening, however, she decided that she would learn to do it herself. She did this about four times and I cheered her on and clapped - she was very proud!
I took these photos with my "rapid fire" function on, so this all happened in about 5 seconds (or less).