Hi! This actually happened a few years ago, but I still don't know if it was a bug or my friend was just messing with me.
We went to play a normal peaceful multiplayer game together (survival server just for the two of us). It was pretty scary, because at that time I heard some stories about Herobrine and I thought he somehow got into our game.. I don't fully remember what we did there, but I do remember those scary moments. So far, I don't really know if my friend was messing with me or if it really happened. My friend created a new world, I think. As soon as we spawned together in the same place, we saw a redstone in front of us. It was pretty scary, because redstone can be shown as a blood too. At first we weren't sure what that meant, so we just destroyed it and moved on. At first we wanted to make a small dwelling underground, so we dug a hole and settled there. I don't quite remember what happened next, but I know that after a while, lava flowed down. Out of nowhere, it simply appeared there and set the forest on fire at the same time. Then came, for me, the scarier scene. I don't know what it was, probably a bug, I thought. I went out of the hole and saw a white figure pulling a piece of wood from a tree and then it disappeared. I don't know what it was, but I know that my friend also died in the near future, so I thought it was her, even though it didn't look like that at all, but I wanted to calm down. Another thing happened that was quite suspicious at the time. It was nothing special, only out of nowhere a block of watermelon appeared in our house. It just showed up between the doors, my friend had a pretty surprised expression, but then I saw that she had a block of watermelon in her hand when she went to put something in the chest, but then it quickly disappeared again. I was also quite naive at the time and thought it was just a coincidence that I might have just overlooked it. Then we moved. We went looking for some new temporary housing, another was in the mountains. It wasn't that high, we just moved out of the woods. There happened to be another thing, probably the most creepy of the whole game in my opinion. I don't know if it really came out of the game, but suddenly it was as if someone was laughing there. It had a voice quite similar to a normal villager, but it was really creepy. I still remember what it sounded like. After a while (I don't remember much of the things we did between those sections, so I'll jump to the "weird ones") we built a permanent house on a small lonely mountain. It was a pretty cute mountain, it was small and there were only trees around. I remember that out of nowhere the windows began to break on their own, just someone or something destroyed the glass. I remember this thing too. I went to fetch wood from the trees next to our house, and so did my friend. I was behind her, so I had a good view of her. I also immediately saw that some unknown force had pushed her down the mountain. Fortunately, she fell into the water. The last thing I remember was this. My friend was going to harvest wood, but somewhere away from our house, and suddenly, according to her, a pack of angry wolves was spawning out of nowhere. Is it possible that wolves can spawn themselves with a 'herobrine wolf' names? Again, I don't know if my friend was messing with me or if it really happened.
Congratulations on having such a great memory. By all accounts Herobrine doesn‘t really exist, so I assume that the alternate explanations are true. Have you thought of asking your friend about it? Even if she was playing tricks on you she might be willing to own up now that years have passed.
She always tells me that she didn't do anything the whole time and that it actually happened, so I don't know what to think. But if nothing like this should have happened in the game, I'm really going to kick her for lying to me for years.