I think a treasure hunt would be a lovely idea, with a gift at the end. If you write really simple clues she can read them herself too which will help to take up some time.
Have a teddy bear's picnic. It can be indoors if too chilly out. Make teddy bear sandwiches with a cookie cutter (and biscuits too!) and have pom bears and things. Play the Teddy Bears Picnic song and let all her teddies 'join in'.
Have a living room disco. Draw the curtains, drape flashing Christmas lights around, get out torches or glow sticks or sparkly ribbons to wave and crank up the cheesy pop. You could let her dress up in one of your fancy tops, maybe paint her nails and do her 'makeup' (I'd never normally approve but as a 'once in a childhood' type treat it could be very special for her) and let her play at being a teenager going dancing.
Bake something ridiculously unhealthy! Chocolate fridge cake is a winner here.
Rearrange all the furniture in her bedroom, even if only temporarily. That can be so exciting when you're little!
Play schools. She can be the teacher and you and the teddies and dolls can be students. Maybe, like it's important for children who are worried about an operation to play hospitals, it will help her to process her feelings about missing school.
If you don't have a dog but she loves animals, maybe look on 'Borrow my Doggy', see if anyone with a friendly pooch is looking for someone to take him a walk.
If she's OK to be doing some rough and tumble, and you really want to go all out, place a double mattress at the foot of the stairs and then 2 or 3 single mattresses going up the staircase to make a mountain. She'll have great fun clambering up and sliding down for an hour or more!
Play a sort of lotto/bingo type game on a walk. She can decide before she goes what she wants to try and spot - a black and white dog, a man on a bicycle, an umbrella, a purple car, a postbox, a yellow flower etc etc... You could even help her find pics online and print/laminate them, and a piece of A4 with the matching pictures set out in a box - maybe 9 or 12 of them. When you go for your walk, as she spots things she was looking for she can take each picture and add it to her 'Found' pile. It can be as simple as swapping them from one pocket to the other, or you give them to her as she finds them. When you get home she can match them to the A4 paper and see if shes found all of them or if she need to keep an eye out another day. This might be good as an ongoing activity as of course she'll be off school for a while, and need distracting over the next few weeks.
Play at 'Going camping' - if you have a tent, pitch it in the living room complete with sleeping bags, pack torches and snacks, play forest sound ambiance and have an adventure. You could even camp in there with her overnight!
Would she like one of those 'colour in' cardboard playhouses/rockets/trains hobbycraft do? They were selling them for £10 when I was last in there. Should keep her occupied for a while if she likes colouring!
You could buy a bag of mixed gemstones, or little plastic penguins or dinosaurs, and freeze them in ice. It'll take a while to do as you'll need to wait for each layer to freeze before adding the next) and then set her the task of excavating them (hint, near a warm radiator, with blunt tools, salt, maybe a hairdyer to be used with careful supervision)
Make giant bubbles at the park. With the kids back at school would be a really good time to do it as otherwise they'll all come running up wanting a go. This is really good but you can make your own at home:
drzigs.com/products/giant-bubble-wand-age-7yrs-to-adult?variant=7355679473723¤cy=GBP&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gclid=Cj0KCQiAhP2BBhDdARIsAJEzXlGA50zWWANmQv4OUgbsfO9hBMlkybnrg0PNkD4p3iZV5c3BqY5vGZUaAihCEALw_wcB