'My fiancé's sister is a mess, and I don't want her at our wedding.'

Planning a wedding can be tricky, particularly when it comes to deciding on the guest list.

So what should you do when your soon-to-be sister-in-law is a threat to your big day running smoothly? Do you omit her name from the invitations and risk igniting the mother of all family dramas? Or do you bite your tongue and invite her, knowing full-well it could come at the cost of your dream wedding?

Watch Mamamia staff reveal their biggest wedding regrets below (post continues after video).

It’s precisely the dilemma Reddit user ‘dontwanttoinvitesil‘ says she’s struggling with right now. Planning to wed her 27-year-old boyfriend in the next year or two, she’s trying to decide whether inviting his drama-magnet sister ‘Stephanie’ is worth it.

My fiance and I have been together for five years. Despite disliking certain things about his siblings, I both love and like them — I love them like family, and I genuinely enjoy being around them.

While three of the fiancé’s four siblings are happily married, his oldest sister Stephanie is still struggling with her longterm relationship ending two years ago.

One of his sisters – “Stephanie” – is 32 and single. The other siblings are married, two with kids and one with their first on the way. Stephanie was engaged for over a decade, but it didn’t work out and they split twoish years ago. She is clearly still hurting.

Last year, the 30 y/o sister – “Brittany” – got married. The night went well overall, but during the reception, Stephanie drank too much and spent a big chunk of the evening crying on my fiance’s shoulder about how she was supposed to be the next one to get married, she misses her ex, etc.

As if disrupting her own sister’s wedding wasn’t bad enough, it turns out Stephanie’s drunken antics have stolen the show at other important family events, too.

One of their brothers & his wife [both 34] have been trying to have another baby for the past year and a half, and it hasn’t been going well. She miscarried three times. The first time she miscarried, the family came together trying to support her and be there for her. But Stephanie was drunk for the whole weekend and went on about her ex. She spent the time explaining how seeing her brother’s wife struggle to get pregnant reminds her that “her biological clock” is ticking and she’ll never find a man to have a baby with her and she was supposed to have a family with her ex.

Then Brittany got pregnant. The baby shower was today and once again, Stephanie drank too much and… you can guess what happened next. It’s already awkward enough for their brother’s wife to watch her SIL’s pregnancy progress despite having her own fertility struggles, and on top of it she has to listen to how Stephanie should’ve been the next one to have a baby and omg “I’m 32 I’m getting so old I need to have one now or else I’ll never be able to have one!”

Unsurprisingly, ‘dontwanttoinvitesil‘ isn’t keen for history to repeat itself when her own big day rolls around.

I’m out of patience. My fiance and I don’t have a date set for our wedding, but we want to be married within the next year or two. I don’t know if I can bank on Stephanie meeting someone who will cause her to drop all of this. I haven’t told my fiancé how I feel because I don’t want to start a fight, and I know that it’ll be an awkward situation for him. I do not want Stephanie crying at our wedding. I do not want to hear about someone spending the whole night comforting her when they should be having fun. I do not want my family to see her crying all over the place.

I’ve thought about showing a picture of Stephanie to the bartender and saying to only serve her one drink an hour or something, but I honestly wouldn’t put it past her to leave and go buy her own booze, or to bring her own with her from the hotel… I don’t think it’s fair that my family or my fiance’s family will have to babysit her all night to make sure she doesn’t leave to get booze. She is not an alcoholic — I’m not a professional but she doesn’t exhibit any of the hallmarks of an alcoholic. She just likes to drink at parties and family get togethers and it never ends well…

She has already ruined a wedding, a baby shower, and inserted herself in another family member’s fertility problems. I don’t want her ruining our big day, too.

So –  what would you do? Invite Stephanie, or conveniently ‘lose her invitation in the mail’? Let us know in the comments below.