In most forms of media, its common to have certain character types or tropes. Japanese anime and manga is no exception to this. This page hopes to show what her personality is and isn't seen as in terms of japanese animation tropes. I also realized that as i was making this, this really only scratches the surface of her being. I feel my essay on stalking and erotomania would be a good follow up piece.
In Japanese animation there are about four types of character tropes commonly seen. While one or two might pop up in a series, i find series with bigger casts tend to rely on these tropes more to differentiate the characters from one another. I also find most of these tropes pop up in regards to female/male relationships and the show has at least some hinted romance. Harem and reverse-harem shows/games benefit the most from this. But i digress, here are the five types: Tsundere, Kuudere, Yandere and lastly Dandere.
Tsundere (ツンデレ) is probably the most popular and widely known character trope for characters in series featuring romance. Derived from irritable (ツンツン) and lovestruck (デレデレ), it describes someone who is initially very cold or rude to the person. Turning their head away, a "hmph" and other such small actions can help to present their tsun side. They then slowly warm up and is friendly or might even crack a smile to their admired one. :D Another easy way to describe this is like two children on a playground. People joke or tease that the one kid picks on the other because they secretly like them.
I feel the closest person to a tsundere in Fairy Tail might be Charle and how she is towards Happy. I can say however is that Juvia does is not a tsundere in the least bit. While she may seem cold in the beginning, she is by no mean to Gray or acts like she dosen't want him. The closest similarity is that she warms up to people...or the "dere dere" side but this aspect is a part of just about every trope covered here. Onto the next!
Kuudere (クーデレ) is a bit of an odd one that i don't see too often. Or at least its not as easily identifiable as the others. In some ways it a subtrope to Tsundere as they share a lot of similarities. Derived from the loan katakana word for cool (クール)and lovestruck (デレデレ), it describes someone who is always in control of their emotions; They have a "cool air" about them. They might seem pragmatic, apathetic and stoic. That is until they let their guard down to someone, and they warm/soften up. They tend to only let this one person or group of persons see this side of them.
I feel the closest example in Fairy Tail might be Kagura. She is very stoic and quiet, however is very loving and friendly to Miliana and eventually Erza. All in all, i don't think this fits Juvia very well. While she can be quiet (shy) she is not very stoic. In her Phantom Lord days she might have been seen as apathetic, however Juvia was quickly drawn out of that shell by the Fairy Tail guild & Gray. She stays that way too, she does not revert back to being apathetic, etc. when people outside the guild are around. Onto the next!
Yandere (ヤンデレ) is a rather fun one for me. Simply because i find it to be a very strange and often scary trope for characters to have. Derived from to be ill (病んでる) and lovestruck (デレデレ), it describes someone who seems sweet and innocent but at the drop of the hat will become violent and overprotective over their loved one(s). They are obsessive, possessive, and have no qualms with taking rivals out....literally if need be.
From what i've seen, the only instances in Fairy Tail i can find of a possible Yandere is during the Tenrou Island arc. Meredy believes Gray has wronged Ultear (someone she treasures) and will take him out without hesitation. Alternatively this could be said for Juvia as well. At the moment Juvia learns of Meredy's motives, she snaps. So much so it scares even the almighty Erza. She attacks Meredy with so much force she could have easily killed her, in fact Mashima's original storyboard had Juvia killing her. However through the power of love, life and friendship they manage to cancel each other out. Juvia goes back to being her old self and Meredy seems to lose her will to kill Gray. Onto the next!
Dandere (ダンデレ) is the last one on our list and should not be confused with Kuudere or Tsundere. Derived from silent or taciturn (黙り) and lovestruck (デレデレ), it describes someone who is antisocial or silent and then changes to be loving and soft. Unlike kuudere they are not apathetic, they are just shy in the beginning and generally wait to be spoken to. Sometimes, they can just be played in a comedic or exaggerated context.
I feel out all of these, Juvia fits this one the most. Juvia was very much anti-social and silent in Phantom Lord. She didn't speak much with the other members of Element 4 or Jose. However once she meets Gray, everything changes. Even before her defeat her demeanor changes with Gray. While still shy, she falls in love at first sight, and would rather leave the fight then harm him. From that point on in the series she is very loving and sweet towards him. She is also used in situations for comedy and often has exaggerated reactions or fantasies. Currently in the series, i would say Juvia is mostly in her lovestruck phase and rarely shows signs of her taciturn side.