How to deal with a teenaged girls "crush"?

I’m 53 years old and recently widowed. I have very poor skills at reading nonverbal cues (body language, eye communication, etc. due to Aspergers Syndrome). For the last several weeks a 17 year old girl who works for me has been showing exceptional interest in me. I thought nothing of it, believing that she was only interested in my teaching and mentoring.

Last night, my late wifes girlfriend told me that this young lady apparantly has romantic ideas towards me and that we have been the subject of gossip among the other young ladies working here for at least a week. This young lady has made no physical advances toward me and I have done nothing to encourage her; nothing improper has occurred.

While she is a lovely young lady, I have no romantic interest in her, or anyone for that matter. My wifes death has permanently closed that part of my life. I enjoy teaching, but if things like this are going to occur I feel that I must isolate myself from it. She may feel some excitement about this, but I feel threatened.

I suppose that things of this nature happen frequently to teachers, counsellors and others who work with young girls; I have no experience with such things. Besides the impossibility of the situation to me (I’m 37 years older than her), there is also the ethics of the matter (I’m her employer) and the potential effect on both our reputations.

How does one go about discouraging her unwanted attentions without hurting her feelings? She is my late wifes niece (daughter of her second cousin). In her culture (rural Quebec), relationships between older men and very young women are common, even encouraged by the economically disadvantaged families of young women. She is a very attractive young lady and has a striking resemblance, physically and in personality, to my late wife at that age (Meghan was 18 when we first met). This only complicates matters for me.

Can I remain her friend and mentor while discouraging her romantic intentions? How would I go about doing this? Would it be proper to use the same channel through which I found out about this to send back a discouraging response? I’m not very good at social communication.