Basically, yes.
Mariah is a variation of
Maria, and I'm certain that I've read that in eighteenth century and early nineteenth century Great Britain,
Maria was usually pronounced the way we pronounce
Mariah today.
I think you can pronounce either whichever of the two ways you want, but people do tend to think of
Maria being ma-REE-ah and
Mariah being ma-RYE-a, so probably best to avoid that headache.
Mariah looks better IMO.