She is a relatively young elementarist mage of friendly nature.
She is very curious (mostly about things, not other peoples' private lives), and can happily talk about languages, magic, plants, animals, odd places...
Politeness and basic manners are a matter of course for her, but formal situations with complex protocol make her nervous. It also seems like she doesn't know about shaking hands.
Nearly all of her clothing is dark blue (a colour restricted to magic-users where she comes from), often with yellow decorations. She carries a shoulder-height staff (polished wood without ornaments) which can act as focus for some of her spells.
She has a decent foundation of school knowledge (but the history, geography and language bits would be of little use here...), but most of her skills lie with magic.
Elements she's familiar enough with for simpler manipulations are water, air, soil and rock. She has some passing acquaintance with metal, and with light where it touches on the domain plants.
Sylvie channels through her palms and fingers. She uses simple gestures.
For more information, see the articles on eodean magic and elementarism.
She hung out at the unnamed Inn for a few days while the wood parts were being fixed, and presumably made the acquaintance of Suitov, Jaina Jade, Basaltine, possibly Agueda and Bowman - but what about Weft during that time? Jaina introduced her to Lance.
She briefly met Sebastian and Weft, who both were not in their usual form, so she's neither feeling like she's going insane, nor death.
Weft confuses her. She had been told he's a murderer, and she saw that he was rather keen on killing a certain griffin-like creature, but on the other hand he'd been obviously concerned about Sebastian, and rather friendly when things calmed down.
Sebastian kindled some curiosity, namely the question: is he that adorable when he's not concussed, too?
Suitov seems like a kindred spirit in that he's curious. On some level his relatively formal manner makes her feel awkward.
Later she did quite a bit of travelling, which is not unusual for young mages.
One job she was given due to her feeling comfortable in the wild would have been obtaining an egg of a small dragon to an older mage, who wanted to make a dragon his familiar. This job was, however, a failure, since the dragon hatched before it could be delivered. Sylvie named it Ayu-Asra and is stuck with it. If someone assumes he was her familiar, she corrects them; he is just a pet.