It looks to me like a rather pale flowered M. laui. The pale flowers worry me and make me think that it might not be a pure form. There have been lots of hybrids between M. laui and M. carmenae, and from somewhere I have a white flowered M. laui in my collection as well as a laui x carmenae, and of course the 3 subspecies.
Do you now the source of the plant? any collection numbers or field data?