How about keeping the Th theme going?
Matthew, Elizabeth, and Dorothea
Matthew, Elizabeth, and Tabitha
Matthew, Elizabeth, and Ruth
Matthew, Elizabeth, and Theodora
Or stay with a fairly classical name theme -
Matthew, Elizabeth, and Alice
Matthew, Elizabeth, and Susannah
Matthew, Elizabeth, and Cecelia
Matthew, Elizabeth, and Tessa
Matthew, Elizabeth, and Greta
Matthew, Elizabeth, and Felicity
Matthew, Elizabeth, and Rosemary
Matthew, Elizabeth, and Annabel