[quote=@KoL]
But, weren't they supposed to be like spell books containing all Magecraft related lore acquired by the family so far? Nevertheless, there's just these persons that can learn lots of stuff very easily, I vem have noted the the only one she's really good at is Bounded Fields, the rest are developing knowledge that she'll master over the course of a few more years/her entire life.

- You mean the chains, or the snake? Because the snake is about as strong as a normal one, while the chains are just capable of following simple commands, but don't have any other special characteristics. I'll try to be more specific later.

Anyway, I really want this character to work, 'cause I like the idea of her, but it's way too hard to make her 100% accurate. It's way too much time spent on that task, so if you have any suggestions to fix her magecraft to around the "genius, but not impossibly OP" level that you would admit for this RP, I'm more than willing to take them.
[/quote]

Was referring to the snek.

Sure, but here's the thing: magus families specialize. The family that does a bunch of things is the family that's a failure. As an example, Kayneth who has a first-rate family, much more education, and may or may not be multicresting depending on how you interpret stuff knows the following: Liquid Manipulation, Spiritual Evocation, and Bounded Field theory. Those are his big ones, and then he has a dash of alchemy and healing tossed in. Zouken, who's lived for several hundred years, can basically have his entire powerset summed up by "Absorption and Familiars (Worms)". 

If you want my advice, it's to pick a theme. It sounds like the transfer of heat and depletion elements are ones you like, so if that's the case then hone in on them. Maybe her family has a Finality that's similar in nature to Depletion Garden (with obvious differences), and her Mystic Codes operate along that same theme. Maybe she knows alchemy, but only uses the theory of it to improve materials to better facilitate heat transfer by lowering their specific energy, and doesn't know much else beyond that. Maybe instead of knowing magecraft for all five elements since that would take forever to learn, she focuses on the ones most related to transfer of heat and collapse of energy. 

Characters in Type-Moon stuff work best when they have one solid theme and stick to it. That's just as true for Servants as it is for Masters. Herc is great because he has a theme, his skills and NPs all work synergistically to make something absurd. Even GO has some examples, like Caesar, who's actually really well-designed as far as his power set goes. The theme should be your focus, instead of trying to make an everyman.