I'm not sure about Sylvies approach to this, and can't really relate since i ain't that short, but i might have a small tip on closing the distance relatively safely in order to use knees.. It might be a bit clumsy to explain this in text, but i'll try.
Try to push your opponent away with a teep, then follow up with a jab, you don't have to hit them with the jab, this is mainly to measure distance and maybe make them shell up a bit, then close the distance with a knee feint with your left knee, use the movement as you put your left foot on the ground again, step to the right of your opponent and try to grab them. Left hand upside down behind their neck, right arm on the outside of their bicep, use your strength to push their head downwards as you would in a normal clinch. If you do this fast enough, you will have very good controll of their body and they are in a pretty vulnerable position to take left knees in the stomach. When they try to push you away, you are also in a pretty good position to follow of with a sweep with your right leg as they step back, you will have maybe a second or so to do this as they gain their composure again, and you are still in the dominant position.
I don't know how much you will understand of this as it is in text, but this has worked pretty good for me against taller opponents. But it is of course not withouts it's risks, every move is possible to counter.
You might want to try this in a shadowbox routine before you apply it to sparring.