Gally's name is changed to Alita. Why this was done is unknown, but the person who decided on the change tried to "validate" it, explaining that coincidentally Alita comes from Russian and has something to do with Mars (which is where Gally is from, incidentally).
[...]
Besides renaming Gally to Alita, the North American version of the manga also changed the city of
Salem to
Tiphares, after Tiferet. Since Kishiro also used the name Jeru for the facility atop Salem,
Jeru was renamed
Ketheres in the translation, after Keter. To further develop the
Biblical theme in the original series, Salem's main computer was named
Melchizedek, "the king of Salem" and "priest to the Most High God".
[...]
In the October 1993 issue of Animerica, Fred Burke, co-translator for the Viz Comics Battle Angel Alita manga explains that, “For a Viz Comic to work, it’s got to appeal to more than just the hard-core manga and anime crowd;” therefore there were several alterations made in the translation of the manga. Yukito Kishiro’s title Gunnm, a compound of Gun Dream, was re-named Battle Angel Alita. Gally, the protagonist, had her name changed to Alita, a name, Burke explains, means “noble:” a name that he discovered while searching through a book of baby names. Burke also explains that, for no reason given, the floating city Zalem was re-named Tiphares: a name meaning “beauty,” taken from the Qabalah and the mystical Tree of Life. Furthermore, Yugo’s name was given a cosmetic change to Hugo for American readers.