Every baby's A time can be different which is why EASY is a routine adapted to individual needs. I would say though to begin with A times based on her adjusted time, she may also need to eat more frequently than every 3hrs. Tracy did mention in her books that the guidance times for ages were based on a fully term baby of average weight. Prem babies will be expected to stay on the lower A and E times for longer, for instance at 4 months 'average' baby will more to a 4 hour EASY, staying awake for 2 hrs and eating every 4 hrs, Tracy said for a prem or low weight baby this transition would be more like 5 or 6 months. As with all babies you need to observe her cues and record her EAS patterns to see what might be tweaked to help the routine.
If your baby has discomfort from gas then I'm afraid you are not going to work out her best A time based on nap length, you could have the perfect A time and she would still wake due to pain. I hope you can get some help with that soon.