M.R.
Although you are self-managed, I am guessing (hoping) that you have an attorney for when you need it. Contact your attorney to best learn how to proceed. You should also be following the association's declaration to the letter. If you haven't already, start documenting everything. Get advice from your retained attorney and try to stay a few steps ahead of the game in case she decides to 'forget to pay' and leave. If she tries to sell her condo and she is delinquent, you can have the attorney slap a lien on her title. I am so sorry you are going through this; I used to be on our condo board (fortunately we had a management team) and I know how 'not fun' this can be.