Still lives with her ex

I have been having a relationship with a divorced woman for the last three years. We get on very well together, enjoy each other's company and have a very active sex life. We are both of mature years. My ladyfriend's ex still lives in her house. They are both going overseas on holiday and to attend their daughter's wedding, staying in the same room in the same hotel. She swears that there is nothing between them, just good friends. Should I continue with this relationship, or would it just be foolish for me to do so?

Stick with her for a while longer. The truth - good or bad - will come out eventually.