Bridesmaid drama help please!

So I have 4 bridesmaids all were asked 5ish months ago wedding is coming up in june and everyone has ordered dresses except for one, who was hesitant from the start because she didnt want to spend 40 bucks for her dress. Here it is in March, I talked to her several days ago and said she would order it either that night or the next night... I asked her to say when it was going to come in because one of the girls dresses that ordered it 5 months agos dress wasnt coming until April. I still have not heard from her. I had a heart to heart with her and said if she didnt want to be a bridesmaid that's ok too shes still welcome to come to the wedding, to which she responded she still wants to be a bridesmaid. I am at a loss. What the heck do I do? I am aware cutting people out is a friendship ender and I dont want that, but what the heck do you do with a person that wont take it upon themselves to order their dress?