Firstly, does your wife know you are thinking about telling your friend? Be sure she is comfortable with you telling your friend before doing anything. Secondly, being her supervisor complicates matters, you are in a position of power over her, so it's not straightforward. You are in the best place to judge how she is likely to react. I think it's the dream of most of us to have female friends we can share this with, but, most women often think men crossdressing is weird and perverted, they are much more accepting of gay men dressing in drag than straight men crossdressing.
Best case scenario she accepts you crossdressing and you can share your crossdressing adventures with her, but, would your wife be happy about this? Worst case scenario she rejects you, tell everyone you know and there might be negative consequences at work, possibly even losing you job, plus the fallout from that on your marriage. It's a massive decision to make, think long and hard about this as you can't undo this. Whatever you decide hope it goes well for you, but, be prepared for possible negative consequences.