I'm trying to figure out who to choose for my references for my application. I already have one professor from undergrad that I'll be using for one of them, plus my current supervisor. I'm unsure about the third, though. I am currently in a temporary position, replacing someone who's on maternity leave. After speaking with my coworker today, she suggested that I could use this person that I've been replacing as my third reference. I feel like I've been doing a good job at keeping things running while she's been away and, while she hasn't been working here at the same time as me, I have been keeping up a regular correspondence with her and have asked her questions on a somewhat regular basis.
Does anyone have any advice? On the one hand, it might be great to use her as a reference. I'm applying for grad school at the same university where I've been working, so she might be able to speak to my ability to handle her position while she was gone. On the other hand, I've only met her a handful of times and it might be better to use someone I actually worked with regularly as a reference.