So these are the only scenarios I can think of (obviously some are outlandish and some have already been dismissed):
1. Went for bike ride and was attacked by animal;
2. Went for bike ride and was abducted by a bad guy;
3. Went for bike ride and became disoriented/ill and is lost;
4. Went for bike ride in order to isolate and harm herself;
5. House broken into by bad guy and she was abducted. (Tons of options here - stranger, spouse’s lover, her lover, either lover’s spouse, former student, etc. )
6. Killed by <modsnip> other close person and bike ride scenario was staged.
Am I missing anything?