[@13org]
I would say...that for the tarot cards, if the information is semi-instant, the information needs to be very vague and simple. Such as "Danger" or "Run" and it doesn't alway come in time to be useful. AKA, I assume that if she did get the word 'poison' it would be only be a minute or so before someone without the power could have worked it out on their own. AKA "So thats why I can't feel my legs". I would also see the tarot cards not being able to say "Hey that snake lady is the cause of the poison" So unless Hissy gave another sign about who was causing it, Shai would just know that somehow someone was using poison. 

There is a lot I like about her as a whole, but I do want to keep things fair. 

As for her mana reserve. I would say yes...but there are some conditions.  First, I would say that she has to be willing for herself to be 'open' in either way. Like, unless she is activating the 'portal' for mana, perhaps no one can us it. And maybe it has to be open in some sense for her to use magic at all. I also think that having a lack magic overloads / outburns should cause her negative effects in the moment, such as pain anytime she uses magic. 

I am not saying these are your have tos, but I am wanting to hear your thoughts.