No, I wasn't confused.
Dorothea comes from Dorotheo and
Theodore comes from
Theodoros. They're the same parts just reversed. So,
Dorothea counts as a feminine form of
Theodore, imo. If it makes you feel better, insert
Theodora, but they have the same root. Just as I would consider
Samantha to be a feminine form of
Samuel, even if it isn't a direct feminine form.
♥ Samantha ♥