Was offered a free photoshoot, what’s the polite thing to do?

Hiii everyone! I just want to start this post off by clarifying that I’ve never had any photoshoots done before, so I’m very new to this whole world. I’m just looking for a little bit of advice on how to go about this situation.

So, a few days ago I reached out to this photographer I saw on instagram because I absolutely adored her photographs, and I was wondering if she could take photographs for my friends and I before prom. To make a short story even shorter, she won’t be in town on the day of my prom, but since I mentioned I’m a senior in high school, she asked if I’d like a senior photoshoot free of charge (she said she’s looking to expand her reach to teens in my town), and I was so completely elated about that and immediately accepted! One of my favorite photographers offering me something so out of this world, you know, that’s what I thought.

That’s where my question comes in. I know she said it was free of charge, but I’m wondering if the polite thing would be to offer to pay? Or tipping, maybe? But if so, how much should I tip? I’m a little worried because I just booked my senior photographer (different one) and it cost me a pretty penny, and especially since I’m paying for it myself, I don’t know if I could afford two different photographers.

Any and all advice would be super duper appreciated, you can probably tell I’m not used to this business😭 Thanks in advance!!!