Eragon first meets Angela in Book 1. She's the herbalist with the werecat, remember? She gets way more noticable and important later, when she turns out to know a lot of magic, saves Eragon repeatedly, and owns the SHARPEST BLADE IN THE WORLD. She calls it Tinkledeath. She studies toads (Frogs!). She has actually befriended a werecat. She must be centuries old, and the elves respect her tremendously. She was taught by an insane magician who may be the most powerful person in Alagaësia, and who might be Eragon the First, though that's just a theory. (According to research I just did, she may also be a Time Lord.) She is one of the most mysterious characters in the series. She may feature in Book 5, which Paolini has been planning. She is AWESOME. 

Okay, done rant.