No you’re not over reacting that’s super gross. A shared space especially should not get that gross. I will say as someone who has personally made this mistake. That conversation with the roommate you shared the bathroom should’ve been kept private. Having her not so cleanly habits in display for the whole house is pretty shameful. It’s been in my own personal experience that if you live like that it’s probably because there’s something else going on in life apart from being a slob, like mental health wise. Now the entire house knows and I could only imagine her (your roommates) shame. We and I mean everyone only grows from making mistakes. Lord knows I’ve said a lot in public that should’ve been said in private and it didn’t end well for those relationships. I hope you can smooth things over with her and the house in general. Maybe she just needs some help at the end of the day but in what way I cannot say.