Shell and Bell have worked out (well, Bell has worked out and Shell has tentatively commented on) a merging protocol that they think will work for them.

Shell's memories are going to be perfectly accessible, but they will not come up automatically in response to stimuli unless the resulting Shell Bell is expressly open to it. They will keep Shell's hard-earned tolerance to pain, insofar as that's separable (Shell is quite sure that she'd be able to make a pentagon if another situation as important as getting ahold of Sherlock to mint Juliet came up). All of Shell's insights about Sherlock's importance stay. Her itchy discomfort with Sherlock not getting her importance will be folded into Bell's resignation to same. The merged Shell Bell will be comfortable referring to either past in the first or third person, but will default to using "I" for Bell and "she" for Shell. She'll torch, but that's the only supernatural property Shell's bringing to the merger; she'll retain all Bell's magic. Shell looks a little older, but not much; they'll go with that, as they think torching probably conflicts with actually aging and they don't think twenty is the ideal place to sit forever and whatever Shell is supposed to be is closer. They are omitting the nightmares, good riddance.

"Last minute questions, comments, reasons to expect this to be a bad idea in some way?" Bell asks.

Shell shakes her head. She is looking forward to not being a separate person anymore.