Mate, having had one of my friends do this exact process over the last couple of weeks, I know the questions you are asking. He looked at a VT 400 and loved it. He could have got a VT 250 second-hand for about $3,000 but eventually bought a brand new VT 400 for $10,000 on road. His argument was that if he had bought the cheaper VT 250 he would have had to sell it at the end of the 12 month learning period and buy a bigger, more expensive bike then, so he might as well get the bigger bike now and simply keep it. Also he wants to take his lady friend on the back but can't till the end of the 2 months, so he's simply getting prepared.
Assuming that Teela won't want to stay on a LAMS bike for any longer than necessary I suppose the best advice would be to get the cheapest LAMS machine you can, and spend the next 12 months saving for what she REALLY wants. There are loads of LAMS bikes at dealers, simply because people trade them in after 12 months, but they do seem to move out of the dealers very quickly, so keep trawling the dealers and snap up the first half-way decent machine you find knowing that you won't have it for long anyway.
Cheers
Whizz