It sounds like you don't trust your sitter. If that's the case, you need to make other arrangements for your childcare. Your child is counting on you to look after his/her safety. You can't be concerned with offending the babysitter.Lots of sick people out there. Home daycares you really can't be sure because most are not audited. But then most home daycares are cheaper than the business type daycares. So you have to weigh your options.
I have a toddler in a home daycare and sometimes I wonder when the woman who is taking care of my child.. when her husband comes home from work.. what really happens. My toddler can not speak yet so who knows what really happens.
You can try to find a new child care provider from your county Certified Child Care Provider list. They will be regularly audited, have to follow state rules, and take ongoing child development/safety classes. It's not a perfect situation, but it sounds better than the setup you have now. Good luck.