Is she paying you anything to use your tools? If not, I would think that you would be entitled to a replacement. If you were allowing me to use your tools without cost, I would want to buy you a new one or fix yours for you!
Can you just purchase the hook side of the Velcro and replace it? Adhesive packages of hook & loop are available in numerous sizes.
“Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety.” Benjamin Franklin