She needs to lean into the push more.
Bend the front knee, position the back knee so she seems to be bracing herself and have her lean into the push.
If you need a bit of help visualizing, I know I'm not always the best at conveying my thoughts through words, try getting up and leaning on your hands against your wall, as though you were pushing it.
You'll notice that your knees are bent to brace yourself and you're leaning into the push.
Does that make sense?