When she asked if you wanted to stay longer, you should have said immediately that you have no more cash to pay for any more time, then you should have started getting ready to leave. You were both silly.
You overran by a hell of a lot the first time. I'm guessing that's why she asked you this time if you wanted to stay longer. She probably figured that the overrun on the first meeting was her fault, so didn't ask for extra on that occasion. This time, at the end of the meeting, she asked you if you wanted to stay longer. Maybe this difference made it a booking extension. Who knows? Maybe she was new and naïve.
When she asked you if you wanted to stay longer, she should have quoted you the new fee, but you also should have made it clear you had no more money and did not want to pay for any more time, and just left. You're both to blame.