|It is never pleasant to have a co-worker who slacks off and then expects others to pick up the slack. Although she is a problem, part of the problem is that you have been doing her work. There has been no reason for her to change.
Your next step depends on your relationship with the owners. If it is open and communicative, you should meet with them, describe your co-worker’s problematic behaviors, and ask for their help.
If your relationship with the owners is more distant, you could create problems for yourself by complaining about this co-worker, especially since she has a special connection to one of them. In this scenario, you should finish all of your work before handling any of your co-worker’s responsibilities. When one of her projects falls through the cracks, you will have an opportunity to let the owners know what has been happening, and you can do so in the context of being a hard-worker rather than a complainer. The owners’ next action will help you determine your next action.