I don't think you were unreasonable OP.
Although if it was me and the queue hadn't moved, I'd have let her go back to her original place in it. Since it had moved significantly I don't think she should have expected to go right to the front of it.
We had an odd situation of someone saving a place in a soft play place last week at half term.
It was crowded and as we paid to go in we were told that they couldn't guarantee us a table or a seat.
Luckily, someone was just standing up to leave as they let us through the inner door, so we walked over to that table. And just as we got there, a woman seated at the next table moved over to it, leaving her friend sitting at her original table, and said "You can't sit here, I'm saving it for my friends, they've just called to say they are about five minutes away."
So in other words, not even in the building yet, or even in the car park. DH and I just looked at each other and sat down anyway, DS was long gone with just his shoes left behind.
And the woman was furious, she started shouting at us that she was saving the table for her friends who were 'only' five minutes away, that we were ignorant, that her friends had four children and a baby to get out of the car and they 'needed' the table and she was saving it for them.
I suggested she fetch the manager over so he could decide who should have the table, customers who had already paid to get in or customers who had not yet arrived, and as it was one of those tables made of two small ones pushed together, DH separated them so her friends could have half.
None of that was good enough so she just stood beside us shouting "ignorant!" until a member of staff told her to stop it or leave. She went back to her original table and her very embarrassed friend.
It wouldn't have been so bad if she'd been saving that table for longer, but she moved over to it about two seconds before we reached it. And her friends arrived about ten minutes later and were fine on the other half of it.