Girlfriend has a best friend beta dude in her age, 18.

Well I know they're just friends all this long etc. so last night a guy I know approaches me and makes humor how he saw her with him after class, and asked where they were going. She said I'm scared to go alone (lives pretty far from downtown) and my friend is walking me home.

We had a chat about a t-shirt I suggested she buyed yesterday when we were out and she did, and said stuff like good choice listening to your man girl etc. and we made some humor, then I popped a little question as humorous saying " Did you find any cute dog to walk you home last night haha?" (she had found a dog once and sent me a video saying it's cute)

and then I filled the text in with some shit about the t-shirt (not mattering rn)

She said "unfortunately no" and continued commenting the shirt.

I asked her if she went home alone and she said "yes isn't it a pity?"

She's lieing over text. What for and how should I progress? calmly confront her about it?