Hi Sairzey. Welcome to you and to Matilda
Matilda sounds wonderful. How lovely that you've a new man in your lives, and that he gets on well with Matilda too.
You could try keeping the door shut, but I doubt it will work long term, and she may simply end up damaging the door or the flooring if she scratches.
Also, looking at this from Matilda's point of view - she was there first, as you rightly point out, and has had access to her Mom, because she wanted your attention, and you've got that wonderful bond between you.
From her point of view, this is not a wicked or mischievous thing. She's doing it because she wants affection, and for cats it's easier to get our attention at night, because we're lying down, we're less threatening, and we're unlikely to be shooting off somewhere.
To keep her shut out, in many respects reinforces to her that you're shutting off a source of love and affection "just because" someone new has turned up in your life.
And I know first hand how it can be to be woken at night when all you want to sleep.
In fact I reckon we all do.
Personally, I welcome it. For me, it means my cats (who are indoor/outdoor) are alive and well (have lost too many in recent years) and that they're choosing to hang out with us to express the fact they love me and my OH. Sometimes they want that reassurance that we're still there, and we still love them (two of ours were semi-feral). That's okay. I can live with that. Each day is precious.
But I know how precious sleep is too.
I get up each day at 5 a.m. for work, so I appreciate not everyone will welcome the interruption or find it quite so flattering as I do.
My best advice would be for both you, and your OH, to ignore Matilda's night time approaches. Don't acknowledge them in any way, except maybe to gently dislodge a paw from whatever orifice she's managed to smack you in, but without in any other way acknowledging it.
Don't speak to her, don't sit up and make a fuss. Maybe draw the duvet up a bit further round your head. Encourage your OH to do the same. When she realizes she's not going to get a reaction, she should give up.
Fingers crossed.
Do you have any piccies of Matilda?