Ah- I understand. Good for you that you were able to work things out. It sounds like you are a very stable individual and it sounds like your husband and yourself have communicated your feelings to each other
I should clarify that when I say to and get it I don't mean to insinuate that you should go people shopping - more that you should take care of you.
I'm happy for your relationship that you are each mature enough to proceed with your decisions to be open to new ideas - that's not particularly easy given society's norms.
The situation that you have now is perfectly acceptable as long as it is acceptable with you. If its not then it simply must change.
If there is a trust issue between you and her that is probably something that should be brought to the table- sooner rather than later. She sounds like friend of yours as well.