my mom's relationship with me makes me uncomfortable

I'm 19, and my mom is 49. For as long as I can remember, my mom and I have been much closer than any other familial relationship I've seen. When she and my biological dad would fight after their divorce, she would constantly vent to me about him, and I would often have to choose sides, which went on until i was 16. I ended up having to become a therapist for her when I was still just a kid. She doesn't do that as much now, but she has other behaviors that make me uncomfortable. She makes me lay with her in bed until she falls asleep, and I have to kiss her cheek. I've expressed discomfort with the fact that she literally has to cuddle me to fall asleep and how I don't understand why she doesn't do it with her (current) husband, but she gets pissed at me if I don't do it. She cuddles with me in public as well, and always wants to hold my hand. She would insist on bathing me and sharing bathrooms with me up until I was 14. The thing that I'm annoyed with the most is that she has a common tendency to slap my ass when she walks by me, not in a discipline way but in an affection way that some couples do. She'll also just grope and touch my ass and when I snap at her to stop, she gets defensive and says "I made you, I can do what I want" then touches me again to prove whatever point she's trying to make. She does none of this with her husband, I hardly ever even see her spend time with him.

I thought all of this was normal for a long time until I brought it up to my friends and they all seem really weirded out. I'm kind of at a loss for how to feel, because on one hand all of her behavior makes me extremely uncomfortable, but on the other hand she's always treated it as if it were normal family things. I feel like it also wouldn't be as bad if I was a kid, but I'm an adult and she still does this.

Am I justified in feeling uncomfortable and grossed out by how she's treated me so far?

TLDR: Mom(49F) keeps treating me(19M) like a close friend or partner instead of her son by touching me, being clingy to me, and venting to me about personal topics. Is this normal?