Wencesla should be the feminine form of
Wenceslaus, which is extremely rare in the Netherlands today, as in 2014 there were less than 5 people with the name in the entire country:
http://www.meertens.knaw.nl/nvb/naam/is/Wencesla (in
Dutch)
As for Yscaira: it definitely is
not a traditional
Dutch name, so I'm thinking it's either foreign (perhaps Latin American, as Google tells me there is a Latino bearer of the name) or invented by the parents. I'm afraid I don't know anything else about it, so if possible, you could ask Yscaira herself where her parents got her name from.
I hope this helped! :)
"It is no measure of health to be well-adjusted to a profoundly sick society." ~ Jiddu Krishnamurti (1895-1986)