RE: Justifying Headcount
Go to the SHRM website & look at HR metrics. There's a lot of different ratios to look at, all based on comparing one factor against another. Every company has some measure of workload, which makes it easy to calculate workload/FTE. She's going to have to show some comparison of the expected workload of an FTE, whether its a comparison between departments, or a comparison with an industry standard. What she's able to calculate will depend on the financials she has access to. For example, she could track payroll costs/FTE as historical data, but I don't think that ratio tells as much as payroll costs as a % of total revenue. She'll need access to revenue to calculate that.
She just needs to look for points of comparison with the information she has available & be creative (but accurate). I recently had a clerical person in one of our offices who kept demanding that she needed a whole department of additional clerical help (reporting to her, of course). I didn't want to prove my point with revenue, because her supervisor doesn't see that info. So I calculated a ratio of clerical hours/client (clients is a measure of our workload). This ratio demonstrated that, compared to the other offices, she was not overworked at all...just inefficient. I liked that ratio so well that I'm going to add it to my metrics for all our offices. It was a very revealing measure of efficiency.
I'm a big fan of metrics. Without them, you have no objective measure to judge by.