Mirta is a hybrid of witch and fairy.
She originally attended Cloudtower for witchcraft with her best friend Lucy, but chose to exchange to Alfea for fairies, where it was more happy and friendly. She's shy but sweet just like Flora.

At the end of season 1, in The FT Squad's Adventures with the Winx Club, Kyle the Otter asks her if she wants to join the FT Squad so that she doesn't get lonely. Mirta will agree, though in seasons 2 and 3, she will keep studying at Alfea, away from the FT Squad as well as keep in touch with Lucy. Nevertheless, she'll still be part of the squadron's travelling team.