The cruise control is a ratchet plate that catches on the edge of speed control arm.
It is held on by one of your favourite items, a spring.
Follow the cruise control rod under the dash and you will see the mechanism.
Because of the angles, it does not work well at either max or min speed but fitting a bigger spring will make it work better.
The caveat to this, a heavier spring will require her to both push the pedal done while pulling the cruise control lever up, it will not automatically dissengage.
Finding the correct parts break down using the cub web site is a PIA but if you care to post the full model number from the tag under the seat we can use the MTD diagrams that are a lot more clear
It should start with 13
