They don't need complicated things.
If she or you have friends with kids, have play dates.
Kids also like "routines" and they get accustomed to it pretty quickly.
Everyday, have a "schedule" or routine.
My son at that age LOVED when only he and I would have breakfast together after taking my older daughter to school. Because it was just he and I. That alone time with me, was what he enjoyed.
Then we'd go home and he'd help me "wipe" tables and while I did the chores.
Then we went to the park.
And on other days the library.
And on other days, collected stuff in our yard and made things with it just gluing it to paper.
And on other days we colored together and made "art." Or painted rocks.
Or I would get some spices together, sprinkle some in a dish and have him smell it and I would tell him what spices they were. Then, I would have him guess which it was by having his eyes closed.
Then it would be nap time.
Kids also need runaround time. At this age. Just physical stuff.
Play ball, by tossing or kicking it to each other. Playing tag. Playing Simon Says etc.
Have simple crafts for her to do. Or decorate and play with big boxes. Kids love that.
Or hide like 5 objects under a towel. Let her look at the objects then have her close her eyes. Then while she is doing that, take 1 object away. Then take the towel away and have her look at the objects and guess, which one is missing.
Make a "path" in your home, with pillows or wash cloths... then let her scamper around the house, just by hopping from pillow to pillow or washcloth to washcloth. Kids love that.
Just think of anything. Main thing it is fun. And it does not have to cost money. I did things like this with my son and daughter when that age.
We would also just lay out on a blanket in the yard and stare up at the sky and I would teach them about clouds/their names and pretend where they might be going. Imagination stuff. Its a good thing.
But yes, kids like routines. Tell her everyday what you might be doing. Kids like to know and they look forward to it. Even it is just something simple.