She needs to know that you are a person with needs just as important as her own, and sometimes you need space to do the things you like to do, and that this doesnt mean in any way that you love her any less.
I'm doing xxx now, please go and find something to do on your own.
I'd like a little space for a cup of tea right now, i'm exhausted and need some me time.
I need to complete xxx task, and you are preventing me by getting in my way. Please go and amuse yourself.
I am busy and unavailable to you til 6pm, please leave me alone until then.
All these should be perfectly acceptable things to say.
Start practicing now and stick with it. Expect her to amuse herself, screen free, every single day for a period of time. It'll be really uncomfortable for both of you for a bit but its much better for her to learn this now, especially as an only.
And yes, if she can't think of anything to do, give her a chore. Not as punishment just as a suggestion if she cant figure it out for herself.