OOC:
Detect magic would tell you that magic is happening w/in 30 feet. In order to outline the item/person, however, you have to see them. Detect Evil and Good would work more like you want. You know she is fey, so you know that it would tell you if she were with 30 feet and where (or at least that A fey was within 30 feet and where). Further out than 30 feet, neither will help as it exceeds their range.
As for audible option, you could do that and make an intimidation check as a regular roll (advantage because holy crap, disadvantage because sound without creature isn't as frightening, so they cancel for a normal roll). However, not sure how intimidated she would be, but you could try.
If you have a sound based AOE attack, that would certainly hit her if she were in range (like Thunderwave or the like).