Sythril Vythethi
Wait. What's going on with Sable?
She's gonna be in Pewter City a while so Darren can grab the Boulder Badge, and then they were gonna head over to claim the Cascade and maybe Thunder badges. Due to Tanabata, a couple of Sable's pokemon got a bit too powerful, and since it'd be easier in the short run to pick up an extra badge or two from Kanto instead of having to get a semi-useless first badge from Unova and then the next one or two she needs for obedience purposes, she's figuring she might as well hang around a while longer and get those badges before heading back to Unova.
If, however, what you're referring to is her uncertainty concerning having her beedrill use a mega stone, short story with a small spoiler is that she has trust issues, mega stones basically work off the trust between trainers and pokemon, and she's aware enough of her issues that she realizes things might not go smoothly if she hands her beedrill that stone.
Well, I apologize for not replying since I have someone in Kalos and, therefore, would have theoretically been an appropriate person to reply, but given I'd personally be more offended if someone said something along the lines of "I do have a character out there, but right now he's in a high-level area despite being a lowbie, I haven't been able to come up with a post for him in at least a month and probably won't be able to do so for a while longer, and depending on how I have this last stretch of what he was doing before I lost motivation go he might be just as likely to try and maim/kill your or anyone else's character as hang out with them, so it's probably not a good idea for our characters to meet up," than just ignoring the post, I didn't think it'd be a good idea to quote you just to give you that sentence and an obligatory "good luck" message.