Thanks for all the advice everyone - I'm working through all the suggestions now.
To answer a couple of Qs - the vocal style would be best described as floaty and ethereal. And, so far, utterly drenched in fx

I'm aware that the latter aspect makes much of the choosing between this or that mic characteristic a bit moot, but I figure start with a good capture of the source and it'll open up possibilities later. If she can hear she sounds good on her own it'll boost confidence etc. At the minute she's just using a mega-cheap dynamic that came with the sampler she's got.
She's been asked to send some vox tracks to a producer/remixer who's heard some of her stuff online, so I kinda want to help with that. May well come to nothing but it warrants something better than that crappy mic she's got at the moment.
Room treatment is an issue so thanks for that heads-up. I'm reading up on that and we'll do what we can, which might not be much but still.
Going to see the 2200A later today. It's pretty old and much-used but he'll demo it for me so I'll take a view on it when I've seen/heard it. I found a comparison vid yesterday of voiceover work with several mics including the SE and it jumped out at me as being rich and well balanced, much nicer than the others (can't remember what they were apart from a samson C01). Meanwhile I'll look into the other suggestions.
Thanks again