So not on her planet. They look human... Could she be in a spirit world? Or - she remembers a theory, vaguely, about the many spheres, each containing different inhabitants. Could they have different magic? In which case the serpentine monster that brought her here is likely a demon from a different sphere, moving sideways...
She doesn't know if their magic is strong enough to seriously injure her. Her soul gem rests at her waist - not the most obvious place to aim, but a broad blast at her chest could get it. She wraps the gem in fabric to muffle the glow, figuring that it's possible they're unfamiliar enough with magical girls to not aim at it - but there's no point in offering a clearly magical shiny as a target.
It doesn't feel like she has any innate healing. Her magic's keeping her body maintained, but - healing effectively will be a skill to learn. So it's possible she'll be injured past her ability to heal without going dangerously low on magic.
...If this sphere lacks witches, then cleansing her soul gem might be a problem.
Maybe there's some skill she can learn with converting magic types. Which means ingratiating or otherwise establishing herself - the hidden people seem to have the most magic granted to common troops, and she's not sure she trusts anyone noble to share.
Plus, ripping people's hearts and magic out seems unnecessarily cruel.
The hidden groups probably have their own plans, but she's going to need to establish herself as on a particular side quickly...
She's not sure how they'll react to telepathy. And it might be best to hide her dousing abilities for now...
She practices flash-stepping very quietly behind her cover for a few seconds. It's far from mastered, being a more difficult skill than dousing, but she gets the basics enough to fling herself far faster than human eyes can follow - tracking her own movement like this will be hard - and next to the priest and the altar. She spins, raises a shimmering barrier of latticework arrows around the prisoner - it's crap, she needs to practice, but hopefully it'll disrupt whatever effect - and kicks the priest (not so hard it'll do more than badly bruise) away, then spins to slam her bow into the men in aprons.
And then she turns and looks straight at the nobles, nocking her bow - which is of a kind she's been practicing with since shortly after she learned to ride. She's about to fire, but the nobles will have a second or three to react before she puts an arrow through the gleeful one's eye. (She's also keeping her emotion sense leveled at every threat in reach, ready to dodge or jump if someone attacks her.)