The allotments have also been the perfect social context for me. I have serious social anxiety, and find it difficult or impossible to join in group things etc and impossible to "socialise", but the relationships that develop between plot neighbours is perfect for me. So yes, not just about veg.
Sorry to hear that is the background to your loss. Maybe you could volunteer or seek out a charity that works outside with people with anxiety issues. There is a scheme which pairs gardeners with older people who can't manage their garden. Just a small space will make a the difference. House plants?