Which one should I take for my senior year- AP Chemistry or AP Psychology?

You don't need a lower level psychology class in order to do well in AP Psychology. AP Psychology is an incredibly easy test a lot of people don't even take the class, read a prep book, and just take the AP Psychology test in May and do well. The class varies in difficulty by high school, but it will still be easier than AP chem regardless of whether you have taken general chem before. AP Chemistry is hard and if you didn't do great in AP Chemistry and all the other kids going into AP chem got As and A+s you will be struggling. I would suggest taking AP psych. When you go to college taking AP psych may actually apply to your major, while general chem will not and you won't get credit for it. Don't drop AP Euro that is actually a very useful class regardless of what you intend to do later on. Another thing to add is since you haven't taken APs before and now you will be taking four you may struggle getting used to the course load. Taking a hard class like AP chem will just make things even harder for you. If you want to take an AP science does your school offer AP Biology (since you said you like Bio) or AP environment (that is an easy AP). Just throwing out suggestions.