I’ve been with my boyfriend since university. When I lost my mum as a child, I took on the adult role of carer for my sick father until he died. My boyfriend is close to his family. They are not financially secure, due to poorly paid jobs and his mum’s shopping addiction, but he supported himself through university and has a job with good prospects. His dad had a stroke and got a £90,000 insurance payout, but luckily he recovered, and put by money for his children’s weddings. His older sister took her share (£5,000), but since then they have spent all the money, including their children’s wedding fund. I’m shocked and saddened, and it’s made me miss my dad, who was generous and left a fair inheritance. My boyfriend wants me to think about marrying him rather than his family, but it’s causing rows between us. I’m afraid they’ll treat their youngest daughter differently when her special day comes. I don’t know if I want to be a part of his family any more and worry the stress will spoil what’s meant to be a magical time.

I’m not sure I entirely understand your problem, but I’m going to tackle it simply because I feel that, unless you change your behaviour, you’re in grave danger of upsetting your boyfriend so badly that your only special day will be the day he tells you that it’s all over.

I wonder why you’re so outraged about people spending money that is theirs to do with as they wish. I know you feel you have a right to it, but, honestly, do you? As you pointed out in your longer letter, the recent economic difficulties mean they may lose their home.

That doesn’t seem to bother you. What’s outraged you is that they used the extra money to buy a £10,000 Jacuzzi and “fund his mum’s consumer-driven lifestyle for a few more months”. I can see why you might think that a foolish extravagance, but we go back to the point that it is their money. When times were easier, they promised to fund their children’s weddings. I agree that a broken promise is irksome, but that still doesn’t give you the right to claim the money as your own. What seems to be driving all this is a pronounced sense of entitlement. You say you’re “shocked and saddened”, that you’re not sure if you can “forgive them” and that their actions are “unfair”. Honestly, there is nothing as unattractive as self-righteousness. It’s a quality almost guaranteed to drive people away, so if you continue with it, you risk alienating not only your boyfriend’s family, but him, too. As you say, it’s already causing rows between you.

That, at the very least, should be a warning signal to shut up and put up. As your boyfriend says, there’s nothing you can do about it and he wants you to think about marrying him rather than his family. You seem so focused on your special day and “magical time” that it seems the wedding matters more than a good relationship with your future husband.

You should be supporting him, not embarrassing him by pointing out his parents’ profligate ways. I’m sure he knows all about that and has accepted his family just as they are. As you say, he’s very close to them.

Do please stop looking at everybody else’s behaviour and examine your own. I wonder if it’s the early loss of your parents that’s the trigger. It’s understandable that you might feel abandoned and want somebody to look after you, but demanding that his parents act as surrogates simply isn’t going to help. It’s tough to feel that you’re on your own without parental support, but you were adult enough to take on the role of caring for your sick father, so I’m sure you’re adult enough to get past this disappointment. Just as I hope you are adult enough to accept that we might have to (or even want to) pay for our own wedding. As your father left you a fair inheritance and your boyfriend is in a job with good prospects, that doesn’t seem too far-fetched. You might find paying for it fantastically liberating. The two of you can do exactly as you please, freed from the tiresome demands of inviting Auntie Edna and Uncle Reg, because the family insists they must be included. In the end, what truly matters is having a great marriage, not having a great wedding.

Watch, too, for jealousy creeping in. You say you’re afraid they’ll treat their youngest daughter differently and are obviously envious of their eldest daughter, who had the expensive wedding you obviously want. Again, that’s understandable if you are missing your father and feel jealous (however unconsciously) that your boyfriend’s father is favouring his daughters in a way you wish your father could favour you. The best advice I can give you is to be very careful. Your current obsession with money and your rights, together with threats about not wanting to be part of his family any more, could do terrible damage to your relationship. There is nothing to say we have to approve of the way families conduct themselves, but we mess with the ties that bind them at our peril.

If you have a relationship question for Sally, e-mail sally.brampton@sunday-times.co.uk. In case of publication, names will be withheld. We’re sorry, but Sally cannot answer letters personally

Times recommends

• How I lost the gift of joy for a while
• How to get Coleen Rooney's post-baby body
• The A-Z of winter style rules