Maybe you mean to ask: What are Spanish variants of the names you give, if there are any?
Jade: I could not find it used as a given name in Spanish, but anyway, the word for jade, the stone, in Spanish is 'jade' as well.
Jen,
Jennifer: According to BtN, this could be
Genoveva in Spanish, if you see
Genevieve as a form of
Guinevere, the "precursor" of
Jennifer, and not as a separate name - click the links to see the information about these names.
Jess,
Jessica: Well, Shakespeare seems to have invented that one, so probably no time yet for the Spanish to develop a separate form. If you look at Iscah, the Hebrew name that maybe was the base for this invention: This name is given in the Spanish bible as Isca.
Christina: That's easy, that would be
Cristina.
Sarah: Zarah and
Zara are Spanish variants of this name, together with the Spanish pet form
Sarita.
Rene www.AboutNames.ch