She finds that mildly irritating for a whole different set of reasons, but it's such an improvement over the alternative that she lets it be. She's very careful not to seem as though she's taking advantage of her new-found position. She demands nothing, and makes only a few careful, diffident suggestions. This will not last forever; no need to burn bridges.
And of course, whenever she receives an email from the Slayer, she responds promptly.
"I am planning to get into a fight with the Phantom of the Promenade a week from Saturday. There is a plan, but if the plan does not go perfectly, someone may find themselves strangled and/or drowned, and I don't know if prom chaperones are required to know CPR. Any chance you could sort of loiter nearby in case?"
Emma takes a second to process this, then asks, "...Phantom of the Promenade? I suppose I don't see why not, as long as it's not on a work night."
"Week from Saturday," repeats Bella. "It's almost certainly a ghost, which haunts prom."
"Cool. Prom starts at eight, I may try to sneak in before then but am pretty unlikely to get strangled or drowned before prom actually starts. Witches will appear on time."
"These witches are the ones I've met? You haven't started a collection since I've seen you?"
"Bargain. But anyway, yeah, still Soph and Alli in the witch department. Thanks for agreeing to stand by, let's hope you're totally unnecessary."
"To what extent are you a secret from my Watcher? Like, did she hire your husband to teach me to hit things by sheer coincidence...?"
"I have not admitted to knowing about you before the Council did; nothing else is particularly secret. I think we're in some sort of 'non Watchers in the know' list in a vault somewhere? Certainly Tamara consulted someone for the name of a trainer reasonably in the know, she did not draw Phil's name from a hat."
"See you then." Emma hangs up and goes off to find herself some books. It appears she'll be having some downtime to read shortly.
The day of the prom Alli shows up at the door to the gym on time, looking surprisingly put together in a slinky black dress and carrying a bouquet of blue irises. No promises will be made as to their non-magical origins.
"Nice dress!" says Soph, early, having arrived with Bella (Bella's sneaking-in method was to drop her sister off and then claim to need the bathroom and not emerge). Soph's dress is blue but includes no red; it's got one sleeve and a light filmy overskirt and a wide sash she's hidden witching supplies in.
"Thanks!" Soph takes them and tucks them into a part of her sash that is not occupied by witching stuff. "Hey," she says to the doorperson. "Can we go in yet?"
"Not without your dates, you can't," the closer boy responds. "Didn't you see the signs? Dates or nothin'."