What kind of swimsuit should I consider in this situation with my friend?

I have a friend and we're going on a road trip to the beach. I need a new swimsuit, and I just lost a bunch of weight, so I'm feeling quite sexy. The friend I'm going with has put on a little weight and she's a little self conscious about her body. Am I going to make her feel bad if I wear some little bitty bikini? Should I stick with something a little more modest to consider her feelings?