Model Managers
Good employees often wonder how to approach their manager about issues and situations that have an effect on their job. For example, I have a part time hourly job and since my boss was going to take a day off, she generously invited me to do the same, seeing I had a very hectic month. Problem was, she was full time, I was not. She could afford to take a day off because she would be getting paid regardless. Whereas, if I did not work, I would not get paid. So I kindly explained this to her in an email and stated that I would be working from home as well as coming into the office throught the weekend. This was a touchy issue as this boss strikes me as the controlling type.
It's understandable that you didn't want to lose the pay for the day - but perhaps it would be better if you just answered the question instead of explaining why. If she's the boss, then surely she realizes that she gets paid for the day and you don't. Reiterating the fact could sound like you're questioning her motives. Perhap a simple and gracious decline would be better received. Something like, "Thank you so much for considering me, but I'll need to decline the offer this time."