Thank you Peep, for posting a different point of view. I hesitated to post more than I had, because Seasider needed support, and I didn't want to appear critical, when she is struggling to enjoy her life with her OH. However, in a general way I'd like to add to the discussion.
I would add that I think certain occasions, such as really important family get-togethers, should be attended if at all possible. People who care about you can help to make them bearable (quiet rooms, sitting near people who understand you etc)
These seem to be the issues:
Mental health: Seasider did say that her OH had depression - although not exactly how he was doing at present - I thought the situation as described quite stressful for someone with any mental health issues.
The social etiquette of such gifts: I thought it an expensive gift for someone who doesn't know them well, and not very thoughtful for someone who did. They may have wanted to give Seasider a treat, not realising that she would have had a nicer evening with a friend.
Finances: It can be difficult to have a separate social life if money is tight. We are fortunate in that we live in an area where the kind of things we like can be enjoyed cheaply.
Myself, I think the issue is communication and understanding. Being the partner of someone with depression can be very difficult. I would hope that Seasider can find a few TV programmes to enjoy (I think there's some great dramas on, but am aware that my taste is very different!), that Seasider can have an occasional treat evening out with friends, and that they might find some evenings out locally that would give them both some pleasure.
I hope I have not overstepped by posting this - I intend no criticism.