I know how that sounds and I feel awful for repeating it. I would appreciate some insight into what others think I should do here.
My sister in law came to our home last week and she was not close to me and I could smell her very bad breath, it was offensively bad and that is an understatement.
It smells like gum disease or something similar along the lines (as she has a couple of other times and I haven’t smelt it but it is the odd once or twice I am really starting to smell it more and more).
We were in my front room and it’s not the largest of sizes and I had to move to our larger kitchen area to get away from the smell. I felt awful.
Husband’s sister is in her early forties and she suffers with Williams Syndrome so it is not like I can mention it to her as she wouldn’t understand and her Mother (my mother in law) is her career who I don’t also feel I can mention it to her with fear of offending her!
The only person is my Husband but I don’t know how he would take it. I don’t know if MIL is just immune to the smell now!
It is not just bad breath but I can smell when she is clearly on her Aunt Flo and there is a very obvious smell of that around her. She is overweight and quite short so I don’t think it helps her 
I am sure my Husband is aware of it already as he has mentioned it to me once about a year or so ago but never again, I get the feeling he is embarrassed as it has gotten progressively worse.
She sometimes needs help to brush her teeth but even with help it’s not being done properly and she needs help to be bathed also otherwise she wouldn’t do it herself.
I know this sounds awful and I don’t mean to come across as spiteful or downright offensive 
I am so sorry if anyone takes this to offence but I am really wondering if I should mention something to my Husband here and as I’m conscious others may start to smell this also around her. AIBU here and should I just let this go?