From Halopedia, the Halo wiki
Isabelle is a Mamore refugee living on Earth in the United States. In 2552, she helped get Kamal Zaman to Pittsburgh in exchange for using his medical expertise to help friends and family, including her cousin Jessie. She had apparently been treating them herself using supplies acquired on the black market. She is unofficially dating Brad.
Isabelle seems to be attracted to Kamal based on the way she talks to him, and her reluctance to admit that Brad is her boyfriend. (i.e. "Do you have a girlfriend?")