Was I wrong for offering a mother to cut me in line?

I'm curious because I felt awkward after this interaction. Earlier today, I 30M was at a coffee shop. I was the only person in line, waiting for a barista to come back to take my order. While waiting, a mother of 2 kids walked in behind me. She was holding one child, and the other was a toddler walking behind her. The conversation went like this:

Me: Ma'am, you're more than welcome to go in front of me

Her: (Confused) I'm sorry, what?

Me: Feel free to order first, I'm in no rush

Her: (With what looked like a disgusted face) Why would I do that?

Me: You'll get your order quicker, If you wanted

Her: Seriously??? With an eye roll and a head shake as if I said something horribly wrong.

I then turned and placed my order. I felt so awkward.

Did I cross some sort of boundary? I thought it was the right thing to do, by letting a mom that clearly had her hands full get her order quicker.