Nope why do you think that she almost killed her ?

The whole Nala and Vitani relationship is made up by the fans. In the movies it is never said that. Are they related? (if that's the thing your talking about) Well, it's up to you. Most peopled needed an explanation for Vitani not looking like her mother Zira so they began to think Vitani is scar and Nala's daughter but Nala had to give her up to Zira for many different reasons. Are these true? Well, these explanations aren't proven. Hope this helps

These stuff are just part of fan fiction. Which is product of other peoples imagination, when people try to expand universe and fill in more information on untold stuff, or sometimes it is part of theorizing to connect some lose ends in TLK universe(Most famous in this is Kopa and movies). But nothing of it is part of official universe.

"Does nala love vitani?" What?! They are both girls, unless you mean like family love, but they aren't family, so no.
"Does nala protect virani?" Err, I'm not quite sure what you mean. I've never seen that in the movie, and what "Nala and Vitani thing" are you talking about, exaclty? You mean as in fanfiction, maybe them being related? If thats what the "thing" is, then no, they aren't related, unless in fanfiction.