Yeah, my older one is that age and wouldn't wear hose, but she would lean towards tights if it's chilly outside. Leggings under a dress or skirt "could" also work with the right outfit or dress.
My older one loves heels, so I know she'd choose those over flats, but I'd probably stuff flats in my bag because at that age, they're still learning that being in heels for hours isn't always the most comfortable thing. Another footwear option can be a dressy boot or bootie. My younger one isn't a girly girl, but I've found her some great boots and booties that go well with dressy clothes.
As for the attire, part of it depends on weather/time of year, but also her preferences. My older one has been known to gravitate towards formal dressy skirts and blouses if it's a cooler month. She did this for several of our fine dining dinners in Vegas last December. She also likes more pop and flash, so we paired more basic, toned down tops and leggings or tights, with sequined or beaded skirts. In warmer months, it's usually some kind of sheath dress. The younger one is more of a dress pants and dressy blouse kind of girl. I convinced her to do dresses and skirts in Vegas last winter, but for her recent formal banquet, she wore a muted snake print pant with a nice black blouse that had a cowl neck and sleeves that ballooned to the cuff.