I actually went through the semi-long process of writing a bunch of games over each other to allow be to put Harle back into the party after she had left. It makes for a very interesting battle with the Dragon God. (Also, a side note, she doesn't say anything if you bring her up tot he Frozen Flame, for somewhat obvious reasons.)
She really is my favorite character both battle-wise and plot-wise. I tend to enjoy people that throw things more than swinging them (I'll pick Van and Doc over Leah and Marcy any day), and throwing small things, such as her little "jingly bells" just adds to my adoration for her. Her speciality techs are well-rounded as well. Moonshine is a lifesaver in some big boss battles, and Lunaretic? Apart from the damage it does, just looks amazing visually. And she flips and what not. I like flips.