Am I wrong to be worried/upset?



My girlfriend and I planned a trip to the beach as our time together—just for her and me (we did have her sister and her sisters boyfriend tag along). However, she was on her phone constantly, always texting her "friend." I don’t mind her texting people, but it was literally all the time.

At one point, we're at the pool, and she asks me to keep an eye on her phone to see if her friend, let's call him David, texts her because he's almost there. I thought, "Who is David?" When I asked, she said he was a friend going to the same college as her. I thought, "Okay, maybe he's chill, and there's nothing to worry about," because you can usually tell if a guy is after a girl. My girlfriend has a ton of guy friends, and I'm fine with most all of them.

When he shows up, he’s always by her side, acting like a puppet to a master. The way he talks and the things he says made it clear he has intentions, if you know what I mean. After dinner, he finally leaves, and I tell her that his presence made me uncomfortable and that I don’t really like him. She says she understands.

Later, we're watching a movie on her laptop, and she goes to get something. Her phone notifications pop up on the laptop, and I see she's texting him everything I told her about feeling uncomfortable. The next day, she invites him again without saying a word to me, knowing it bothered me. I only found out minutes before he arrived, and she acted like it was the most normal thing ever.

I tried to bear with it, but when we got back to where we were staying, I went to our room, expecting some time with her alone. She never joined me. When I checked the living room, she was sitting next to him on the couch, so close they were touching. I walked back to the room, feeling really frustrated. She texted me, "What's wrong?" and I responded, "Where are you at?" She replied, "Well, my friend is here, so I'm going to spend time with him." At that point, I decided not to poke the sleeping dragon.
Updates
1 y
1st Update
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So I thought after things had cooled down a bit and we all got back from the trip, I would bring it up to her. So I did. I first started by saying I had a few things I wanted to talk about and if we could talk in private. She agreed. I started by asking; "How are we doing?" She responded with; "I don't know." I asked what had been bothering her and she responded by saying she was upset that I was "moody." And to be fair, I rarely am "moody." I tend to see the best in things.
Updates
1 y
1st Update Continued
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I've been trying my best through the last few years to do so. But this time along, I let it get the best of me and overthinking took the wheel. So I responded to her saying I was "moody" because David had shown up unannounced, some guy friend I didn't know and for a moment overthinking got the best of me, so I felt down and went quiet and didn't participate in much (do note that I am prone to sun poisoning if I am exposed to direct sunlight for more than 30 minutes).
Am I wrong to be worried/upset?
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