Hi, don't mind me, I'm just dropping plot ideas for Tilly here as I think of them. Feel free to DM me on discord if you're interested!
I really like the idea of Tilly having a best friend who doesn't use magic. A vampire, an alien, whatever, and preferably someone who's more of a jock archetype for contrast. My vision for their relationship would be a shared love of something nerdy, like DnD or Warhammer, or one of Tilly's athletic interest, like running or fencing, and that they push her into social settings that she would usually rather avoid. Preferably, they know almost nothing about magic, and don't really have an interest in learning, but enjoy helping Tilly out on her dangerous fetch quests and bailing her out of the stupid holes she digs herself into. And, obviously, anybody who screws with this friend are going to learn the old adage about meddling in the affairs of wizards. Tilly can be distant and reclusive, so this person would have to be the type who doesn't mind kicking in her door and inviting themselves in to check on her. They can expect to receive Tilly's enchanting and alchemy services on-demand, as well as to be a guinea pig for some of her more risky experiments.
Tilly is an okay fencer, but it's more of a hobby for her. As she's learning more and more in her physical altercations, she is not strong enough to face down her enemies unarmed, and she can't always rely on her limited stores of magic. I'd like for someone to take her under their wing and teach her how to fight with a sword, and possibly a quarterstaff. If her mentor is skilled in European-styled swordsmanship, I'll probably have her learn to use a rapier, but if her mentor is an eastern-style swordsman, I'll probably have her use a cool hybrid style with a cavalry saber. I also think it'd be really cool if they either bestowed an old weapon upon her or helped her to forge a new one
In a month or so, when Tilly graduates and starts college, I plan on her to get a tiny upstairs or basement apartment, preferably apart of someone else's place. I'd love for the ensuing drama of her magic occasionally shorting out their electronics and generally being a nuisance. Also roommate plots are always fun in general.
I've left most of Tilly's backstory intentionally vague, but I'd love for her to have a sister who is a natural prodigy with magic, utilizing a style more reminiscent of the "Mana bar" variety, whose gifts come very naturally. Their personality and whatnot can be left pretty open to interpretation, but I imagine they'd disapprove of a lot of Tilly's shadier bids for power, especially her current arrangement with Caissa, and they would probably bicker and argue a lot. Despite that, I really want a close, wholesome relationship for the two of them. Despite their disapproval and Tilly's jealousy of their power, they always have each other's back. You know, the usual mushy stuff. You can basically do whatever you want with this, except I'd like for them to follow Tilly's naming scheme (Named after figures with some association to magic, two middle names that are both kept secret. Tilly's names are inspired by Matilda from the movie Matilda, and the famous magicians Dorothy Dietrich, Charlotte Pendragon, and Harry Bouton Blackstone.)