<human>: **Guys! Thanks for the input, but I think I've got it figured out. Please, for the sake of my inbox, stop telling me to walk/get a bike/stop complaining! I am fully aware of the fact that I could easily just suck it up and walk. The question was not "How do I get to work?" I just wanted some advice on how to discuss this kind of thing in a minimally offensive manner. Anyway, advice received and appreciated. That is all.**

I (21f) have no permanent car. Sometimes I can borrow one, and drive myself to work; those times, I'm always perfectly on time and often the first one in the office. This has been commented upon several times. I get uncomfortable when I'm late to things, particularly when it reflects on my perceived level of responsibility, so I'm generally quite punctual.

Due to my lack of a regular car, I've been sharing rides with a friend of mine (22f) who also works for the same company. We've known each other for two years or so. She lives a few minutes away, and I split gas; it's really not out of her way at all... but she's got a problem with being 10-15 minutes late pretty much every day. Every day this week, she was late, making me equally late. Today, one of our coworkers pulled me aside and said, "Are you starting to run into traffic, or something? I don't understand why you're late every day now." 

Basically, I've talked to my friend about the issue, and she's said she'll try to be more on time. It hasn't happened yet. But I don't know how I can explain this to my boss or my coworkers - who are beginning to get annoyed with both of us - without essentially saying, "Don't blame me, it's her fault!" I don't want to throw my friend under the bus, and I don't want to come off like someone trying to avoid responsibility. 

Help?

Could you distill the essence of the text into 1-3 sentences?
<bot>: I'm ride-sharing with a friend. She's always late, despite being asked to be more on time. How do I explain to my boss/coworkers that I'm not deliberately being late?