Put yourself in her shoes. She likely found it difficult to believe you would take her back, or not be judgemental of her, or forgive her...so many different fears for her to overcome.
I also had a similar conversation with my wife about her saying "I love you," first. In fact almost word for word on both sides. Stick with it and remind her occasionally when sshe falls back into old patterns, just as she should remind you when you fall back onto old patterns as well. : )
Experience is a brutal teacher, but you learn. My God, do you learn. - C.S. Lewis
Life is usually all about how you handle Plan B. - Jack3Beans
Listen without defending; Speak without offending - FaithinAK