Not by herself, but Cersei wasn't the only one who took it that way; that was how pretty much everybody interpreted it, including Stannis himself.We can't take anything Cersei says as truth though, she'd see slights where there were none.
This isn't really disputed by anyone. Robert blamed Stannis for the Targaryens escaping Dragonstone, even though they had left the island long before Stannis' fleet could have been ready to sail.