Millà is a Catalan form of Émilien (which means, yes, male) where it is pronounced with a Y sound for the L but that's down to one king's lisp enforcement and if the whole of South America can ignore it so can we ;o) Outside of Spain, the L sound applies. (Even in Spain I found that people understood my South American Spanish just fine and I say all the L's and C isn't TH - no problems)
Also Milla occurs as a short form of Ludmila, etc. in Russian and Polish and has been used as given name from the Slavic element meaning 'grace, favour'.
In Czech Republic it's a short form of Milan/Milana, etc. Dh's uncle in Prague is Milan and his wife calls him 'Mila' though I personally think it works better on the girls.
And yes, in English, it's a short form of Camilla and occasionally of Millicent :o)