This is terrible thing to happen Sheamus and it was why I mentioned the importance of having a legal contract. Because of the lack of this, you are indeed vulnerable, and your housemate knows this, and she knows exactly what she can do and is taking advantage of your vulnerability. Regardless of her age, it makes no difference. Such people will always be that way and probably always where. You're much younger but have the wisdom of an older person, and she's like the opposite, an older person with a young person's mentality. Age really doesn't mean better character.
I've indeed often suffered enormously for speaking out and still do. Many hate it when people speak their mind and give them a hard time, often in a very sneaky unethical way, as they know the person who speaks their mind is honest. Recently I've had some upsetting situations and one last week in particular, which made me feel also insecure in my home and not at peace. This was over a very toxic relationship with a particular person has always exploited any vulnerability. The good thing at least is that I don't live with the person and have trying to get them to block me, so that there is no contact, and I think the feelings are mutual. We just don't get along and there have always been problems from the time I remember but they can get very stressful and out of control. It's very tough dealing with this feeling of "fight or flight" and feeling fearful, but you have a RIGHT to speak your mind. Your flat mate never cared about your consent and although you thought you sorted it out a while ago, over the frying pan not being cleaned, I didn't think it would be as simple as that. Boundaries have been breached and you have a right to your boundaries. I hope the situation will resolve itself and at least you have your girlfriend to support you.