It's definitely strange and invasive behavior. And you never have to ask if you are "allowed" to feel annoyed, or any other emotion. How something makes you feel isn't for anyone else to judge.
One thing I'll say, as a fellow home-share host. If you feel like you have to hide away in your room to stay out of a guest's way or because they make you uncomfortable in your own home, then you need to learn some skills for making your boundaries clear, assessing which guests you can be relaxed and chatty with and which ones may be likely to take simple friendliness as a invitation to over-familiarity.
If a guest is doing something which annoys you or is clearly against your house rules or helping themselves to your food or toiletries, it's important to let them know, in a tactful way, right away- letting it fester, not saying anything, hiding yourself away, will make home-sharing a difficult and unpleasant experience.
It doesn't have to be confrontational- sometimes you can even use humor and then just move on to something else, so it doesn't seem like some attack- "Hey dude, I couldn't help notice that your bathroom aim isn't great- girls sit down to pee, you know. How about wiping down the toilet seat with those bleach wipes under the sink when you're finished? Hey, did you have time to check out that nice little cafe around the corner I told you about?"
@Stephanie1750