She will sense what's going on. It is usually apparent when one person that you are close to is deceitful. I figured it out. From experience, It feels pretty devastating. She will need to be able to confide in you about it and you can be there for her. It's a disturbing place to be in when you know about something like this. Hearts are broken and the person who is breaking that heart doesn't really care. They are selfcentered to do this in the first place. warm thoughts.