“I do not attempt to deny," said she, "that I think very highly of him -- that I greatly esteem, that I like him” (Chapter 4)

I think Elinor’s explanation of her feelings for Edward after offending Marianne by saying the above show that she is already emotionally invested but I agree with you that she attempts to control her emotions because he has not declared himself and a practical consideration of the obstacles that stand in the way of a marriage between them. I think there is a difference in not emotionally investing and checking your emotions--trying to not let them grow without encouragement. I think Elinor’s statement, “In my heart I feel little -- scarcely any doubt of his preference”—Chapter 4, shows that she does believe he has affection for her and consequently she has affection for him as she told Marianne:

“Believe them to be stronger than I have declared; believe them, in short, to be such as his merit, (Who doubts Edward’s merit?) and the suspicion -- the hope of his affection for me may warrant, without imprudence or folly.” (Chapter 4)