This whole thread reminds me of when, after I had redecorated my lounge and had a new suite delivered, I had taken some pictures to work.
Everyone kept saying "wow, your house is so clean" and by the time the fifth person said it, I was quite paranoid. Luckily this person was also a good friend so after she also made a comment, I told her that everyone had been saying this and asked her if people thought I lived in sh1t. Well, she roared with laughter, because my poor little neurodiverse brain really thought that but she explained that people usually say that when their houses aren't quite the same!
I just like cleaning and seeing the results which are immediate!
With regard to the bathroom bin and the tampons and condoms. I doubt very much that MIL raked through the bin, she probably saw that it was full and needed emptying.
Two of my children that still live at home have periods and they have to put their used sanitary products outside immediately. I also buy them scented nappy bags to put the products in before they throw them away.
I think to be having menstrual blood and seminal fluids in the bin for 5 days is way too long and also a biohazard.
I get that the bin has a lid, but if it's the only bathroom in the apartment and guests have to use it, then I'm sure it would be quite simple for either you or DH to put your rubbish in the bins on the way out to work in the mornings.
If I went to someone's house and had to put something in the bathroom bin and saw used sanitary products and condoms in the bin, I would also take the bag out, tie it up and ask where the outside bin is. Because it's a biohazard. I'm not knocking the OP, I would just worry about that from a clinical point of view.
Also to add, I've never had anyone take my tidying up of their home in a bad way. Possibly because my friends all know what I'm like by now but also because it's not a judgement, it's to help that person.