My direct report wants a promotion and it's draining me.

She switched to my management a year ago and said that this type of management is what she's wanted for years. Coworkers have commented on the improvement in her working style. I spend large amounts of time coaching this report, gathering feedback from senior leadership about what they can do to work at the next level and how I can support them. I provide guidance on how to produce quality work at the next level. I cut back their other projects so they can deliver on the big project. After our meetings, there is often a need for a lengthy follow-up in yet another meeting. There have been a lot of emotions and frustration expressed. The report feels they are being singled out for not being promoted and over-scruntinized. She complained about the previous manager for months. When I make suggestions, there is always a response for why it is already done. Everyone else I have managed and currently manage finds my approach beneficial to their career. People are clamoring to be on my team as I treat people well and look out for them. This report is starting to affect my wellbeing. People say they leave bad managers. This interaction is one reason I would think about leaving. I've decided to tone back my input as the emotional energy used up is draining me. I guess I'm asking for advice from managers who tried their best and yet it still it isn't enough.