The dilemma My cousin and I were extremely close growing up as neither of us had brothers or sisters. We spent summer holidays together and went away abroad together with our families, too.

As we’ve grown older, we have drifted apart and she has now started a family of her own. Next spring she is getting married to her partner of seven years. She informed me that my partner, and the partners of our other cousins (of which there are many – our mothers come from a family of six), would not be invited to the wedding.

I am deeply angry and hurt about this. I live with my partner and love him deeply. We have a clear future together and hope to marry at some point, too. We were told it is to do with the size of the venue and the cost, but neither of them is short of money. They both have very good jobs. Their friends will be invited with their partners.

I feel she is treating me and our other cousins, who are all in their 20s and 30s, like children. My parents’ Save the Date card from her included me! I am almost 30 and feel completely humiliated at the prospect of attending her wedding with my parents, rather than my partner. How do I put my point of view across without upsetting her or damaging our relationship even further?

Mariella replies With great difficulty. It may not be ideal but, as you point out, it’s her wedding and she can be as selective as she likes. The whole business of inviting one partner and not the other is fraught with social difficulty at the best of times. Few of us want to be joined at the hip, but the choice as to whether or not your other half accompanies you would ideally be up to you.

Naturally, at work functions and on single sex outings, there’s a free pass to exclude those who don’t qualify, but when it comes to social events there’s a controlling, manipulative and even cruel bent to choosing one half of a couple over the other.

I have a married friend who automatically dumps all invitations addressed only to her in the bin, which may not be the most considered approach, but it certainly solves the problem! Personally, having spent some time as a singleton, attending a party on my own is my natural habitat, but not everyone likes to operate as a lone ranger.

There’s a cruel bent to choosing one half of a couple, but it’s your cousin’s day

All that said, a wedding can be expensive and fraught with challenges and how this couple chooses to prioritise their money is not your concern. Perhaps with such a large extended family your cousin and her beau have decided to make it predominantly a gathering of those of paramount importance to their lives together, along with a small minority of those they have to invite. Like it or not, you fall into the latter category. When you hail from a big family it can be difficult to escape them. Seats fill up quickly. That can be frustrating and expensive.

Rather like Noah and his Ark, when embarking on a new phase of life, you should really be free to do the casting of companions yourself. If that’s their ethos it’s a choice you should respect and understand, rather than feel “humiliated” by. You are not a child, so the idea that you would experience humiliation about your partner not being invited, or that you would attend with your parents, seems extreme.

Outlining the stability of your own union as a qualification is also not something you need to be concerned with. As you point out, not one of her cousins is being given a plus-one so her choice to exclude your other half is not personal and shouldn’t be considered as such. As an adult you are free to do entirely as you choose, eschewing convention and even family ties if you so decide.

A wedding is a celebration of the union of two individuals. It’s also, at it’s best, the coming together of two families and two sets of friends, but that’s not compulsory. So often the pomp and ceremony we attach to the occasion can obscure the simple ethos behind the day, which is to gather together those you love to witness your promises and help to hold you to them when the going gets tough.

Your cousin may not have chosen as you would in terms of a guest list, but it’s her day and she should be free to plan it as she desires. If you choose to have a conversation with her about it, I suggest you don’t do so from a position of frustration, anger or humiliation, none of which are justified emotions. Instead you should be telling her that you totally understand the challenges, in particular the desire to please everybody, but that as you consider your partner a part of her extended family you would have loved it if he could have attended.

The alternative is to politely decline the invitation, citing a prior engagement that can’t be avoided – maybe an invented invitation from his side of the family. Either way, you haven’t been singled out, or infantilised and it’s not a comment on the durability of your own relationship. In short, I suggest you focus on her and her big day and put your own insecurities aside, certainly until after the wedding.

If you have a dilemma, send a brief email to mariella.frostrup@observer.co.uk. Follow her on Twitter @mariellaf1