Acantha, Allegra, Angelica, Artemisia, Aubretia, Aviva, Benedicta, Calista, Calixta, Camellia, Cassandra, Cassia, Clarisse, Corisande, Danica, Demelza, Edith, Frederika, Gabriela, Gwendolen, Ianthe (eye-anth-ee), Ivelisse, Jamila, Jasmina, Judith, Kezia, Leandra, Liliana, Lucasta, Lysandra, Mariska, Medora, Melisande, Rosalia, Roxana, Saskia, Scarlet/Scarlett, Silvana, Sylvia, Theodosia, Tullia, Veronique, Violet, Violetta, Z?lie, Zephyrine, Zora
If you want to use Anika, I think you should, and I wouldn't advise changing the spelling, because while it may make sure people pronounce the name the right way the first time, it usually doesn't look good. It shouldn't be too hard to just tell them the correct pronounciation.
Just so people know, Nikita is actually a male name, as in http://en.wikipedia.org/wiki/Nikita Khrushchev

