Not trying to be funny, but have her sit on it wearing track bottoms or anything like that, slippery and stretchy, and see if it helps, her jeans seem tight.
If I sit on my bike with normal jeans I become quite shorter than when wearing riding jeans or motorcycle pants. A pair of nice riding jeans like Dainese that have a little stretch in that area might help before changing the bike.
Can’t understand how you can’t lower the front too, do the forks not go across the top yoke?