'She was doing her job' sounds more natural to me. If you just wanted to imply that she was at her workplace that afternoon though, you could also say 'she was at work', which would be the most natural way to say it.
The structure of your other sentences is incorrect. It should for example:
- 'my previous university was boring': this implies that the whole experience of being at that university was boring.
- or 'i was bored of my previous university': this implies you might have enjoyed your time there initially, but you became bored of it after spending a long time there.
Hope that helps!