She does notice; her eyes glint with emotion just briefly. Sayaka did something truly regrettable. For her, Mami isn't dead-- for her, Mami has just started to tempt the two girls with magic.

"I don't know what you're talking about. Furthermore... you became a magical girl. I should have taken the similar care I took with Madoka-- that's my fault."

She doesn't look particularly guilty about it, though.