Yes, it will make a difference. She has to convince herself that it will. She knows it will!

She has  to know it will.   Just because she has never opened up to him, doesn't mean she doesn't know her Dad.  In spite of her previous unwillingness to accept his love, he always continued to love her.  That was true then ---and that is true now.  She can't let doubt rule this moment.   She is certain he loved her …and if he ever makes it through this, she'll be there to tell him she loves him too. "Oh, God, please give me a chance to tell him!"