Two possibilities:

1. That person is having some mental health issues. If that's the case, I can't say any more than that, I probably know less than you do on the subject.

2. Second possibility. That person is committing fraud. In auditing, one clue, that someone is committing fraud, is that they're not taking their vacation when they're supposed to, and they're not letting others do their work.

Four possibilities:

1. A simple oversight.

2. That person is depressed or has some other issue.

3. She may not like the quality of your work.

4. Fourth possibility. That person is committing fraud. In auditing, one clue, that someone is committing fraud, is that they're not taking their vacation when they're supposed to, and they're not letting others do their work, for fear that their fraud/embezzlement could be discovered.

Whichever it is, it's very unlikely that this has anything with you. It's a possibility, yes, but only a very tiny one.