This is one that all new employers face. Three things are important to remember. First of all, a helper is not a houseguest. She is an employee. Thus you do not need to be “social” and you can (should) keep a reasonable distance. By all means be friendly (highly encourage it), but remember that you cannot be too close to comfort.
Secondly, and perhaps a bit contradictory to the first point, get to know your helper beyond “hello”. Just like you would with a close colleague at work, you need to dig a bit deeper than basic etiquette requires. While, again, you should not be best friends, you should not be strangers either. Try to strike a balance.
Thirdly, a good helper knows when to “fade away” into the background and not hang around in the living room. If this is not quite working, let her know how you want things; when you want to be left alone and when she can come in and clean. She may try her best but she is not a mind reader.
Some employers find that they become very close with their helpers. My wife and our helper talk almost every day after she comes home from work. They discuss the kids and generally chatter away in the kitchen for a bit to debrief and plan. Thus we are certainly close with our helper.
While I’m not suggesting everyone needs to be as casual as our family, frequent and frank communication helps remove awkwardness and make keep things clear and organized.
Unfortunately there are many who still find a helper “uncomfortable” after months and even years. This is not good. Chemistry is important. If you are uncomfortable with a person you may never truly trust her, and you certainly won’t be able to relax in your own home. Try to find a helper you have good chemistry with and build up the relationship until she feels like a natural part of your household.