Seven letters.
The clue reads: the gift she'd never buy herself. Seven letters. She's been meaning to for years. You know the answer before you've found a pencil, because you've watched her stop at the nice journals in a shop, feel the cover and put it back.
She does the crossword in pen. She saves the good notebook for later. She'd love to write some of it down, and there's always a better use for the money. Try JOURNAL. Try MOMENTO. Both fit, and only one of you is going to buy it.

