Ivelisse (also spelled Ivelis, Yvelisse, etc.) has been well-used among Hispanics in the USA and in parts of Latin
America (especially Puerto
Rico and the Dominican Republic) since at least 1960. It seems to be a 20th-century creation blending
Yvette or Yveline with the -lis or -is endings popular for feminine names in Latin
America. There may be a literary or pop culture origin in Puerto
Rico, but if so I haven't yet been able to discover it. There is an outside chance it's someone's reactivation of a rare medieval French name, but I haven't been able to find any references to it in French name books.
I'm surprised that "no one she ever knew" had the name, because it's not hard to find examples of accomplished Puerto Rican women on the web named Ivelisse. Here are a few:
http://en.wikipedia.org/wiki/Ivelisse_Echevarria
http://www.itl.nist.gov/div898/bios/aviles.html
http://www.artepublico.puertorico.pr/english/artistas/jimenez_ivelisse/index.htm#biografia
http://www.bu.edu/dbin/anatneuro/our_people/faculty/sanchez.php