I am starting to plan my son's first birthday party. It will be on a Saturday. Our nanny works Monday-Friday. She is MORE than welcome to attend the birthday party but she is definitely not obligated. (1) If I invite her, will she feel obligated to attend? (2) If she attends, should I think about paying for her time? Will she feel like she's working? Or will she be offended that I am not treating her like a guest?

Honestly, I am ok with any of these outcomes, but am not sure what is SOP for this stuff. I just don't want to offend her.