I've done a bit of googling and research on Nilupa. From what I can gather, it is used in Sri Lanka and it could have been used by the Sinhalese people. The gender of Nilupa from what I've found is masculine, not feminine.
Unfortunately, I couldn't be able to find the meaning of this name, however the pronunciation of this name is, most likely, nee-loo-pa.
Overall, the info that I've got about Nilupa is different from yours.
Hope that (sort of) helps.
~I might be dumb, but I ain't stupid~
My pinool:
http://www.behindthename.com/pnl/149249