suggestions on how to say "please leave now".

Some of these responses are hilarious!

Back when I was married and we'd have friends over, I remember once when it was getting late and the group had moved into the hall but showed not much sign of going any further, I literally said "Right! Time to go!' and made shooing motions with my arms! 🤣

Honestly, if they're staying longer than you agreed, just say it's time to go now as you need to do.. whatever. If you're close as a family it's fine to say that. And if you're not, then who cares anyway!

"Gosh, is that the time?! Look how long we've kept you chatting, I'd better get your coat before we start again".

"Well I can't tell you how lovely it's been to catch up with you today, seeing as we're off out in a bit I'd better run you home/take you to the train".

Ah, the subterfuge! How very British! When inviting someone for a visit that doesn't include an overnight, I think it's best to state an arrival time AND a departure time. "Would you like to come for Sunday lunch? I was thinking from 11.30 until 4pm? How would that suit you?"

And when people are staying, it's important to be clear about the day and time of departure. "Would you like to come for Christmas? Anytime after 11 am on the 24th is fine for us, Can you stay until the 27th? Hopefully we can have lunch together on the 27th before you leave, if that suits you? We'll need to be free by 4 so we can get on with our jobs and chores."

Maybe it sounds a bit direct, but at least everyone knows where they stand!

My friend just gets up turns the light off and goes upstairs when she's bored of visitors, then shouts back down 'let yourself out' ! 😂

Draw a pentagram on the middle of the front room carpet and say "now is the time to summon Beelzebub" ...

A friend's Labrador used to hop on the sofa and ease the occupants , who had outstayed their welcome, off the end!

I find entering the room naked and saying “Right then…” works a treat.

I am a MiL. I live alone and being with people is a huge relief that I look forward to. I try not to outstay my welcome, i.e. I leave before I want to as I know that guests smell like dead fish after three days. But I have sympathy with OP's MiL. Just ask when she is going home.

"I feel visited enough now" is usually quite effective...

If I said "whelp" to anyone I know, they'd think I was having a stroke. What an odd thing to say, unless you're talking about puppies being born!

Put the chairs upended on the table, and start making cocoa.

I am sorry MIL but I am getting a migraine and I really need to go to bed now.

Don't you think it would be a good idea to leave now, the nights are drawing in and I worry when you are driving in the dark.

It has been so lovely to see you today, I have boxed up some leftovers for your dinner tomorrow as well as a few homemade pastries. I would take then out to your car but I am running and bath. Drop the latch on you way out.

OR: Straight for the throat:
Don't you have a home to go to ffs?!?

My PILs would consider themselves very polite people (and they are) but they have no awareness of social cues around outstaying their welcome. They also drink incredibly slowly so a final drink is a terrible way to get them to leave. I don't understand how they can be so lacking in awareness - oblivious to several people around them yawning and conversation trailing off.

Maybe a bit more context needed like will she be leaving towards bed time, has she travelled far?
I think if it’s late into the evening an easy stretch and yawn and “gosh this has been lovely but I’m shattered, you don’t mind do you if I start getting ready for bed?”
If earlier in the day, I liked the idea a previous poster had, something like “how can I get you a cup of tea before you head off on your journey?” Is brilliant.

It is hard work though isn’t it. I used to have two close friends and fortnightly we’d alternately go for a weeknight dinner at each others houses. Whenever I went to theirs, by 10pm I’d be thanking them for a lovely evening and heading out. But when they’d come to mine it was always so hard to get them to leave. It would reach 11pm and I’d literally start getting my pajamas on (I’d say “just popping to the loo and I might clean my teeth and get my pjs on whilst I’m up!”) and they still wouldn’t get the hint. They’ve both moved away now and aside from once yearly weekends away together, all our catch ups are on zoom so I can leave when I’m ready 🤣

"Do you want a cup of tea before you leave?"

I tend to use “shall I make you one last drink before you go?” - it’s quite gentle but seems to do the trick!

We don't know if it is just a one day visit, or one over Christmas. So cannot think of a suggestion.

Oh, just thought - say would you excuse me, I am not feeling too good, I am just going to go lie down, it was lovely to see you.

I once said to DP’s cousin ‘dear god, will you never leave?’

Brutal, maybe, but it was 2.30 in the morning, and we’d been on the go for 14 hours, we’d finally inched from the lounge to the hallway, when she starts wanging on about some fresh nonsense, while her feral kids were getting their fourth second wind and were clearly winding up for more mayhem.

Sometimes, subtlety needs to move aside and make way for directness.

I have been known to leave the guests with DH having said, 'Well, I need to walk the dogs - I'll say goodbye now as I expect you'll be gone by the time I get back!'

But sometimes I think I need a little sign that will gradually glow brighter that says, 'Dear guests, we love you but can you PLEASE fuck off NOW?'

I go for "Do you have to be heading off now, MIL, or are you free to stay and babysit the kids for a bit? I've got a bit of a headache, nothing I couldn't have struggled though, but if you're at a loose end tonight, maybe you could do dinner and bath for them while I rest? What's that? You need to get home to check the house? Oh shame! Ah well, don't worry about me, I'll swallow some ibuprofen and crack on, been through worse."

Do you mean she overstays her welcome by days (travels) or hours (lives locally)? If days, you can plan something (or make it up) that clearly cannot include her. If hours, it’s a tricky one.

Offer to drive them back at x time. Or would you to take x snacks for your journey in the morning. I can help you pack do you have any washing you’d like me to do before you go??

This. Use a sentence that includes "before you leave" would you like x/y/z.