I am sick of carrying coworkers weight

I am sick of doing other coworkers work due to them procrastinating. I work in a three man department consisting of my supervisor, me, and a lady I share an office with. She has been procrastinating getting these monthly reports done. She use to have the excuse she didn't have all the data to do them. But now she has all the data. They have to be done in June because they have to be billed to medicaid in June. So yesterday she is sitting at her desk talking to her sister and then working on her luminary for the cancer walk this weekend. I ended up working on the reports, because the Psychiatrist is one of the people to sign off on them and he is only here on Tuesday. Tuesday is the 30th so I have to voucher them for that day so it is in June. If they don't get done the associate director will come down to our office to lecture us and I hate getting harassed.