SPSS will do what you want, and is quite easy to use. So if it'll make her happy to use a real stats program instead of excel, there's no reason not to. It'll probablly take you twice as long to do simple things in SPSS than in Excel, but that's probablly still less time than it would take you to convince your boss she's wrong

.
The advantage to SPSS is that if you want to do some more complicated analysis later on, you'll already have the files loaded in and ready to go. It doesn't take long to get into areas where SPSS is better than Excel, or into things that Excel just can't do.