Yep, definitely MeerAY.
It is very pretty. I first heard it on a sweet little Yorkshire Terrier whose teeth I cleaned when I worked at the vet clinic. I'll never forget that, because the dog aspirated as it was recovering and I felt so guilty. (She was fine though.) I think the name is too nice for a dog.
I think if you spell it
Mireille, most people will get the prn right -- even folks at the clinic seemed to pick it up fast, and some of them were numskulls. If not, I think the best Anglicized spelling would be Mirae, as far as the prn being intuitive.
- chazda