What does it mean?

He may be a player, or he may be keeping options open or he may be trying to figure out the messages YOU send like;
Maybe he thought it would be a date, then you bought a second, maybe he thought
1️⃣ you were trying to shove him off on another person,
2️⃣ Maybe you brought an extra set of eyes to feel him out and wanted to make a good impression so she'd give the go ahead,
3️⃣ Maybe he thought you were testing him on being friends with your friends. And I've been in a situation where I was on a date and a second woman was brought along to test my flexibility. I did not do well on that test, though as a silent expectation was that I'd cover everyone's lunch, but I took it as 3 means we all go dutch.
I get this since you say her flirted with you but conversed with her.
option 4️⃣ is that he might just be a big ol' flirt and does it with everybody, 4B might be that he's a hound dog after every quail he sees, but he could be a #4 w/o being a #4B.

You don't know what this means, and are asking us or are you just basically bragging about someone flirting with you in front of your bff??? SMH

He might be planning for both of you, one then the other type thing

I dont know. I came here just to see your photo and read conversations. 🙄

nope he just a fuckboy.

I'd see that as a red flag.