Mitko - Well you see, it's because there's gendering in some Mandarin characters ( which are commonly applied to names ). So, because the name "Monica" is typically associated with femininity, I think "妮" is supposedly the correct word. The one you used is more like the masculine variant ( for example, it would be used as the "ní" in "Nicholas" instead, if that makes any sense ). Hope this helps. 😀
