Help...How do I get rid of Mylee's Bottle

Well It has happened...I have a 2 year old still drinking from a baby bottle. I am so eating my words because I said I would never let that happen. Mylee loves her baby bottle. She will not drink milk for me or her daddy out of anything else. She wants it in the morning and at night. When she is tired she wants it in the car. She does drink from a sippy cup and open cup though. I need suggestions. Yesterday I bought her a "big girl bottle" and last night she took a couple sips out of it and said "I not want it big girl bottle! NO WAY!" So I caved and put it back into her bottle. Any suggestions? This is her only Comfort item, she has no other attachments.