This drives me crazy in mixed. I don't normally play mixed but Saturday I played in a big tennis round robin put on by my local league where you could end up with mixed sex partners and/or opponents. On one point I missed a relatively easy sitter overhead wide because I was focusing too much on NOT hitting the woman directly in front of me who was planted inside the service box. She was my same NTRP level and had no intention of bailing out but I couldn't bring myself to aim at her feet as I would have with a guy across the net.
If it was me in her position I know I would have gotten the hell out of there but she was apparently counting on me not hitting at her or maybe in the women's leagues she normally plays in they don't hit near each other.
When should you serve and volley in doubles? Only when you want to win.