But she doesn't flat out say she is bisexual. She says that she has "spent time" with a couple. Well, for one, it doesn't state their gender - they could have been two dudes for all we know. Even if one of those two were a women, that doesn't mean she is attracted to women. For a person who uses sex as a tool, attraction and orientation don't come into it.
I'm sorry but, yes it does. Even if you use sex for a coping mechanism you are going to look for things that do it for you( things you find attractive or turn you on ). No one just decides hey, I'm sad, depressed, suicidal I'm going to use sex as a coping mechanism and sleep with a gender, or person that I don't find attractive or sexually appealing.
Furthermore, yes I would use a mod to make Jack Bi, it's not destroying the integrity of the character or her story.