Wits end..

[Bibanova]

Partner’s 11-year-old daughter visits regularly/stays with us and there are ongoing issues around boundaries. She often speaks rudely to her dad and spends a lot of time on her phone, including at the dinner table and late at night.

I’ve suggested simple house rules like no phone at mealtimes and no phone after 9pm. She’s made it clear she doesn’t think she should follow these as I’m not her parent. Her dad is reluctant to enforce any rules, saying he doesn’t want to cause conflict.

The result is tension between us whenever I try to set boundaries, and he frames it as “a problem between the two of us” rather than addressing the behaviour.

Has anyone dealt with this successfully? How do you set and maintain boundaries for a child in a blended family when the biological parent doesn’t back you up?
Am I being unreasonable to want harmony in my own home?

It's difficult setting rules for his child that he's not backing up.. but you can if it's your home. "No phones after 9pm in this house" so it's more "house rules" which you're more in your right to set.
The dad sounds more lazy than anything as he can't be bothered to implement anything.

So this child’s mother is also being undermined by his lazy arse parenting.

He is the problem and you can’t pick up his parenting slack.

There is always a price to pay for the path of least resistance, urgh feckless fathers.

This

Ah, a classic case of Divorced Parent Guilt Syndrome. Not much you can do about it really, except speak (gently) to your DH about it and take the long view. The divorce wars are a powerful motivator and neither parent wants to be the Bad Parent which will make the other look better.

My DH was so afraid of losing the divorce war by being the bad guy that when DSS brought home head lice we waited several weeks to treat him because DH didn't want to ruin his weekends with us. His mum finally treated him, but DH and I had already caught it and I turned out to be badly allergic, and it then took even longer to clear because DH didn't want to inconvenience DSS with the combing while he was, say, playing a computer game or watching tv. The only reason DH took any action at all was my throwing a fit about it.

In general, I dealt with this sort of thing by reminding myself that I was not DSS's mum, but more like an aunt: definitely within the family unit, but not a rule-setter. I think the only time I ever told DSS to do, or not do, something was when I got him to stop kicking my chair while I was wfh... and if memory serves, I bribed him. 😂

Have you tried explaining to him that he is not doing her any favours by letting her do as she pleases. That he’s doing more harm than good? You probably have I was just thinking if you frame it that the rules, boundaries etc are best for her, it might make him take more responsibility.

It must be maddening that he won’t even match the rules her mum has in place for you and her mum.

The dad is being a wimp and raising a little madam.
personally I don’t think I could be around this and would leave