The bill of sale can be recognised as a contract and you can sue her for any outstanding amount as well as legal fees, that is if she s still in the country. If she leaves then simply take the business back somehow.
Julie,First of all you should create such a good business realtionship with her that she should think twice b4 running.And u should proove her that cheating u is not a right thing to do Some times our attitude helps us not the court
Your associate is bound by contract to make the monthly payment. SInce she has defaulted, you have every right to take legal action.
you take her to court and they will settle it