chances are she isn't going to change her ways.
chances are she didn't "give or cause "your bipolar.
whether she is stigmatizing mental illness is not erven the issue...she has her own issues as due you.

are your children bothered by her attitudes? do they come home from visits upset? if not maybe suggest a shorter visit say of a few days, since perhaps it is your feelings that you are applying to the visit. if the worst she does is be over concerned with table manners, kids can adjust and deal for a few days. , if the rest of the visit is fun for them. will she take them for trips? have fun activities? don't let your feelings cloud over what facts there are for the visit.

what will it accomplish to confront her? other then to deal with your feelings? if she is ocd confronting her is not going to solve her ocd. and if she is older (and it sounds like she is) it might make the condition worse, since you are confronting her and she may not be willing or able or willing to change what has been her norm for a lifetime.

just because it bothers YOU does not mean it is the right action to change something in another person.

would your children be in DANGER during the visit? if not then why stop the visit?