I'm not suggesting you are kids, I'm just saying that it isn't something you can fix. This is an issue of money. Get an estimate if you want, or go over to home depot, find a similar top, and offer 25% of the cost to the owners. That is more than they should get from the deal in my opinion, especially if they are going to turn around and rent the place to someone else. Chances are, the owners would just pocket the money and live with the damage, (like I would, if it were my rental.)
DO NOT attempt to have the vanity replaced yourself. It will cost you more money than you are liable for here, and it shouldn't be replaced for cosmetic reasons alone if the place is a rental.
I am not being flippant with you, and even if you didn't like my first answer, it is what it is. You learned not to put acetone on plastic, and the owner will learn not to rent his property out if he can't handle cosmetic accidents.
I wish you the best, really. Offer them money, and go home.