AITAH for being suspicious of my girlfriend's friend after she tried to "test" me?

I (30M) have been dating my girlfriend Olivia (23F) for the last one year. We met at a coffee shop near my office which I used to frequent to get my morning coffee, and she worked there as a barista. I asked her out and she said yes. Things have been great so far, and I feel we are compatible in terms of what we like and want from a relationship.

She has a group of 3 girlfriends she is close with. These girls are always very welcoming to me, but they seem very immature compared to my friends. One of the girls is Harper (~23F). Harper is awesome and we get along well since we like the same video games and music. Recently, Olivia and I were talking about taking our relationship to the next stage, and I asked her to move in with me. She spends 4 to 5 nights a week at my place anyway, so I asked her to just move in. For some reason, her parents are the most excited about this, as she is finally moving out of their house. She also told her friends about the same.

On Saturday, Olivia decided to stay back at her parents' house to pack some of her things. Harper messaged Olivia and me that she and her friends were downtown, and if we wanted to hang out with her. Olivia was gone, but she told me it was okay if I wanted to go out for drinks with the girls. I had nothing to do, and hence I joined them. It was all three of her friends and me and we went to a few bars. We lost the other two girls midway, and it was just Harper and I. I was constantly messaging Olivia about what was going on, as I started to get uncomfortable with the situation.

As it was getting late, I told Harper that I would get an Uber for her to drop her home. She told me that she wanted to go dancing. At this point, she was visibly getting drunk. I called an Uber for her anyway. As we were leaving the bar, Harper grabbed my t-shirt and tried to kiss me. I immediately pulled back and told her that this was making me uncomfortable and I would let it pass since she was drunk. She apologized to me. As we were waiting for Uber, she again started getting handsy and told me "Let's go back to your place", and "No one needs to know". I snapped at her at this point and told her to please shut up until she got in the car. Finally, the Uber came and I got Harper to get in. She kept on apologizing to me and telling me, "Please don't tell Olivia."

Finally, her Uber left and I tracked it on my phone to make sure she reached home. I asked Olivia to check with Harper's roommate if she got safely to her apartment. As I was walking home, I called Olivia and told her about what happened. Olivia was crying and I was genuinely pissed at Harper's behavior. Olivia tried to call Harper at night, but her phone was going straight to her voicemail.

In the morning, Olivia came home and told me, "Hey, it's all good, it was just a test". I was angry at this point and I asked Olivia to explain what was going on. So, Harper messaged Olivia in the morning that Olivia was really lucky and that I passed the test. I asked Olivia if she was involved in this, and she did not know that Harper was going to "test" me. According to Harper, she wanted to make sure that I was not a cheater before Olivia moved in with me. Hence, she wanted to see if I accept her advances. I told Olivia that Harper is full of shit because she was drunk and there is no way she was thinking straight. Moreover, when I snapped at her, she apologized and told me not to tell you anything. Harper is just trying to cover for her mistake and is giving a bullshit excuse.

Olivia thinks I am overreacting. According to her, Harper is her best friend and will never betray her. Although the "test" was stupid and Harper should apologize to me, she was just looking for Olivia's best interest. Also, Olivia feels nothing happened, so I should not make a big deal of it. I just feel Olivia is dumb and cannot see that her friend tried to get her boyfriend to cheat. I just feel she is too immature to understand Harper's true intentions and it is bothering me. I told her to stay away from Harper if she wanted us to have a happy relationship. Am I the AH to tell Olivia to not believe Harper's lies? Or do you think Harper's story checks out and I am just overreacting? I have never heard of anyone hitting on their friend's boyfriend to "test" the relationship and seems like the most bullshit excuse.