Aimbu to refuse to give mil keys to my house

[Belame]

Long story short, my MIL moved to live near us. She stayed with us (in a 2 bed flat - me + dp + 8 month old baby) sleeping on a mattress in the living room for a few days and just when I thought we got rid of her, my DP says to me that because there's no Internet he'll give his keys to my flat to his mum so that whilst we're away (we're going away tomorrow for a week) she can come and use Internet. He also said that she's going to pop down tomorrow at 9am (we have to leave at 10), I'm absolutely fuming. After 4 days disruption, I just wanted to spend tonoght and tomorrow morning with my baby and packing, which I haven't been able to do so with MIL staying over. Her stay really disrupted my little ones routine and I just want my uninterrupted morning cuddles with my baby. Am I right to be so a against it?

She can get a mobile dongle or use an Internet cafe. I'd nip that in the bud there and then. Oh, and I adore my MIL but she has always had a great sense of boundaries.

It´s one morning and then you are off on holiday. Presumably she is getting internet put into her new flat? So it is just a temporary thing. Having someone to stay for four days is really not a big deal. You have years of morning cuddles with your child. You can manage having someone else around for a few of those days. YABU.

Depends what she'll be doing while you're away, if other MIL with keys whilst family are on hols MN threads are anything to go by, you'll have all your cupboards rearranged as well as wardrobes and bedside drawers. All washing will be ironed and put in the wrong place. All of your post will be read, your bank statements physical and online will have been accessed. Your curtains will have been changed to suit her tastes, ditto arrangement of furniture in every room.
On your arrival home she will greet you with a huge smile and say she's "helped" around the house while you were away.

Or she may be a normal human being who will not snoop or take it upon herself to interfere

But really she does not need internet access via your home at all.

Just tell him that you don’t want anyone in your home while you are not there. Put your foot down.

Is it really a hardship as you'll not be there?

Anyone other than me completely confused about who is moving house to where?

No way would I allow this.

Why do families find it hard to communicate boundaries.
My mil knew where they were because I communicated them to her, dh, and later the dc.
I knew what her boundaries were and whilst we aren't bosom buddies we respect each others position.
Only you know what she's like, I wouldn't trust mine with a key and like her at a distance, but you seem to like her living with you, so it's hardly surprising she wants to use the place whilst your away.
You have to set your boundaries and communicate them.