Good grief LapLap - you hardly seem to need suggestions.

FWIW - Early November in Tokyo usually feels great to me. Cool, but fine. I imagine that anyone else from England would feel the same.

Some things that came to mind -

http://www.jnto.go.jp/eng/indepth/seasonal/seasons.html

Foliage is beautiful - but you probably don't want to do that for a whole week. So she might want to spend time in a "normal" hotel in a city - Hiroshima / Kyoto / whatever

The idea of going to Kyushu sounds good - with that length of time she could fly to the South (maybe even visit Yakushima) then work her way Nortwards. Take a direct flight from Fukuoka to Narita on the morning of her last day - should be a good connection for her flight to LHR.

But really it's not that cold on the Pacific side of Honshu. If she wants to see the foliage, then she'll have to stay in Honshu I think....