Some people may seem friendly to others, but they may be hypocritical. You can't tell her everything, because she may betray you in the blink of an eye. One of the most important things is that you can't tell others about your private affairs or some opinions about your colleagues and friends, because this person may become a great speaker and even make many enemies for you, which is very terrible.
Do more things in your work or life, talk less and talk less about others, because you don't know if you can offend some people, and some villains can't. Being kind to others is true kindness, not hypocrisy. If you are hypocritical, you will capsize in the gutter sooner or later, and you will lose popular support.