I prefer Dahlia over Selma. While similar, Dahlia can force them to pill, something Selma cannot do. Now do not misconstrue my words, Selma is great, but 8 power over 7, and boosting your own pills is different from taking away the opponents. While 5 damage for a 5 star is bad, you should be pill manip-ing so it shouldn't matter. This is preference however, just my opinion.
Another suggestion is Sheryl to Calliope in case of a loss, and Amiral Coco to Hawkins Noel. Or Sheryl to Dahlia and Andsom to Hawkins Noel, because Pirahnas can pull off 4 two stars. Again, preference.