She doesn't have an answer to fireballs without super on reaction. She has to resort to spin knuckle or jumping. Both can be baited and punished on reaction for big damage. Her footsie game is strong but not good enough to deal with Ryu when you factor in fireballs in combination with his strong normals. Her low health combined with Ryu's high damage output and her having to take bigger risks to get damage gives Ryu the advantage imo, though I'd say it's 6:4 his favor at the worst.
It feels like 6:4 on the dot to me but imo her worst is Ken, that's closer to 7:3 in my experience. His dps are better than Ryu's, his anti airs absolutely destroy her, he has easy/high stun + dmg confirms including from lights, that dash, he has a better dive kick and... I need an adult. You really, really, really have to get max damage from your blocked DP punishes to even have a chance. If not? Enjoy losing in 2 combos.