[@Necrophage]

There are some restrictions about this ability.

As you may know, shadows.... duh. Cast a light magic and she will be forced to leave the invisibility state.
Even in her aura mode, although light sources are not very effective, a good light magic can create a "shadow free" zone around you, basically  forcing her to step out of the shadows to attack you, giving you a brief window to react.

No shadows mean no shadow walking.

Also, about being undetectable, Tex accepted it. I even asked him before about "tracking magic" because I originally wanted her to have an equipment, something like an magic compass, able to track down people.

and this was his response:
"The only item that tracks arcane energy is useless for tracking people. There are however mages who can track humans based on their arcane signature, but their abilities are VERY limited, and act more like sonar. It is possible to feel Ki in some cases if your ki manipulation is great, but you can only tell how powerful a person's ki is, and the general direction that they are in."

I don't think that its that huge of a deal to make her undetectable while shadow walking, otherwise her role as an infiltrator would be kinda useless wouldn't it?? if people could just feel her magical presence.