Oh jeez, this is what happens when a chapter comes out and there is 4 pages of comments to read. My 2 cents: Yuu's reaction was very normal, Touko was kinda unrealistic. How can she not know, Yuu is hurt and that she needs to clarify what she meant? Ugh
So I've seen this sentiment on Touko going around quite a bit, and although it has been addressed in previous comments by someone else, I want to share some of my opinions on the subject:
Touko really didn't have much to say at that moment. You can tell by her initial reaction to the confession in Chapter 34 that she has noticed how much she's hurt Yuu and immediately apologized for it. And as she herself points out in this chapter, clarifying anything wouldn't actually help, it'll be more like rubbing salt on the wound.
"Hey,you know, I didn't actually mean to reject you, but I'm going to reject you again now"
That doesn't seem like a good idea. Touko is obviously still in love with Yuu, but much like Yuu, she's really not that sharp on her own emotions. I feel like people still retain the image of the perfect and mature sister-Touko, and a large part of that is how it managed to still stick with her after her major epiphany. Her understanding in emotions seems to be only about a tiny bit above Yuu, but a lot more selfish.
Their relationship has never been healthy, and Touko entered it assuming that Yuu would never fall for anyone, something that Yuu actually said, without expecting her to change. Her "I love you"s are small attempts that she thought would ensure this one-way relationship to continue. The "terms and conditions" of this relationship of theirs have been established as early as chapter 10, and it does make sense for Touko to consider this in the logical way as written in her "contract", while still showing uncertainties about her current situations and decisions. IMO the following "I miss her" means way more than what she thinks Yuu should THEORETICALLY mean to her now, but it didn't seem to connect the same way with some people.
TL;DR: Come on she can finally stop being her dead sister let her have some time to learn. It isn't a very fun process but it'll eventually work out.