Because the "Shameless" star shares an unequivocal love for fashion.
In an interview published Friday, Rossum tells Daily News TV critic Ellen Gray, "Dressing up is really fun, has always been fun for me. I love fashion, I love clothes, I love having that Cinderella moment where you get to borrow something and then it turns into a pumpkin and you give it back."
The star was an instant sartorial style hit on the red carpet after she starred as Christine in The Phantom of the Opera in 2004. Since then, Rossum has become a staple celebrity at fashion weeks, making best-dressed lists left and right. She cleans up really well at appearances, although we can't say that's the case for her on-screen character Fiona Gallagher. Read more, here.