At the annual summer party of our company I have introduced a friend and colleague of mine to my supervisor. My colleague is from another department at another office and we have known each other some time before beginning to work at our current firm.
The next day she told me that he found his behavior extremely obtrusive, with him staying in her proximity throughout the whole evening and bringing her drinks, even though she clearly stated that she did not want to drink.
My superior has since then messaged her about once every two weeks, first via corporate email and then privately via facebook, although she has not accepted his friend invite.
The problem arises from the fact that she told me several times how uncomfortable she is with the situation and I got the feeling that she is expecting me to do something about it.
When I asked my colleague whether she has yet given him a clear rejection or sign of lacking interest she told me that up until this point she did just ignore him. I asked this question as a hint, since I figured that it is quite hard to infer a lack of interest when it is not clearly stated. While it may be obvious to her and me (for several reasons, with the main reason being that she is enganged and into wedding preparations), it may not be to him.
I do not want to approach my boss with this issue, since that may damage our professional relationship and I do not feel like it is the right way. Apart from that issue I have always experienced him as very professional person and as suitable for his position.
How can I politely - without damaging our friendship - tell my coworker that she should give him a clear rejection instead of just ignoring him and handle the situation by herself this way, with me available for advice?