No, her soul gem does not have that much capacity.

"Huh. Okay, could she have healed me when she first found me?"

Yes.

"Okay so that's something...why isn't magic common knowledge?"

Most people don't have the potential to make wishes. Those people can't see me, or witches.

"But magical girls could tell them, right? ...How long have there been magical girls?"

Longer than recorded history!

"But the closest thing to legends we have about magical girls are anime...or, no, there's lots of legends that could be attributed to magical girls...if the phenomena of 'witches' has be been going on longer than recorded history, who decided that the English word 'witch' should be attached to it?"

Its etymological predecessors have been used for the species since Latin was spoken.

"Huh. Okay, who decided that the relevant Latin word should be attached to it?"

A Roman magical girl!

"Huh. What're they called in German?"

Hexen.

"That is way cooler than 'witch'. What does it mean to germanophones who aren't magical girls?"

"Witch".

"Where did that come from, originally?"

Where did what come from?

"Using the word 'hexen' for the magical phenomenon."

A magical girl in Germany began using it in 1398.

"Hm. Are there any words for the phenomenon that don't mean 'witch'?"

Some words more closely translate as 'demon'.

"Okay this is probably all linguistically plausible. It still doesn't explain why this isn't common knowledge by now but what can you do. Um...I got sidetracked. Are there any facts about magical girls, witches, or magic in general that you can think I would plausibly want to know and haven't asked about yet?"

Magical girls can do magic relating to their wish more efficiently than girls with different wishes. I don't think your sister has enough to bring more people back from the dead but she might be good at healing.

"That is good to know."

"Definitely." Hugs hugs hugs.

...Eventually, though, Emily will dowse with her embaubled soul gem to find the nearest witch.