Can You Keep Merengue Is The Fridge?

you can but may go soft or soggy
if this is a topping i would make it seperate and keep it in an airtight container till serving, it will keep for quite a while so can be made in advance, then assemble just before serving

Yes, in fact meringue has to be refrigerated or it will go bad pretty fast. Let it cool about an hour first, though.