The passage Kathleen quoted does not use those words, and they aren't really appropriate for Marianne. Vivacious implies being outgoing, and Marianne is really not. She does not go out of her way to speak to people if she either dislikes or does not care about them. Also, although she is very enthusiastic about her own interests, I don't think that is the same as 'fun-loving'. In fact, I often think that hanging around with Marianne would be the opposite of fun, because she is so serious about everything that is important to her. An example would be Edward reading the poetry. To me, a fun-loving person would get a good laugh out of someone trying to read poetry but who was not that good at it (for a modern-day equivalent, think karoke performance), rather than wringing their hands in despair at it.

The problem with Marianne's feelings always being on display is that while she prides herself on having stronger and deeper feelings than other people, her display of feelings often hurts, offends or makes other people uncomfortable. Someone with true delicacy of feelings would consider the effect her words were going to have on others before blurting out everything that crosses her mind.