Sorry for the really delayed comments! Hope this isn't too late to be helpful.
Maya, really interesting project idea. It seems like you have a couple different aims. One is to understand what your study population, postpartum Latina women, define and understand as healthy behavior and what they see as barriers and facilitators to achieving healthy behaviors. Another goal seems more focused on gathering data about the actual behaviors of your study population during and post pregnancy. The last (and it sounds like maybe most important) aim is get input on an intervention your team has already developed. Maybe it would be helpful to break up your focus group into 2 sessions to cover those differing objectives.
It may help to ask the participants how they would feel about a telephone intervention, as well as the content of the narratives.