This name can be found spelled in any of the following ways:
Mahvash, Mahvesh, Mahvish, Mahwash, Mahwesh, Mahwish, Mahwush,
Mehvash, Mehvesh, Mehvish, Mehwash, Mehwesh, Mehwish
(Translating vowels between alphabets is always the problem.)
All versions are acceptable. Just pick the one you like.