My daughter is younger, ony 5, but when we do laundry and fold clothes, we fold outfits together, tops folded inside the matching bottoms, then there is no issue with not matching. Ask her if she would like you to help create outfits and fold them this way, even include the matching socks if you want. Also I put similar types of outfits in the same drawer - leggings with their matching long sleeves in one drawer, capris with short sleeves in another, skirts, tights and shirts in another, shorts and tank tops in another, and jeans and sweatshirts in another. Then she just needs to choose the right drawer based on temperature, and pick whichever whole ensemble that is already put together.
If she doesn't like what she has available, maybe a shopping spree where she really has some say so would be a good idea for Christmas or Birthday gift. And if she does like her mixed up outfits, encourage her to go with it! Just ask her, and try to support her in what she wants and needs, as long as it is age-appropriate and weather appropriate, she is 7 let her have fun with it, she doesn't need to look like a catalog kid!
Good Luck!
Jessie