How long does it take to unlearn bad swim habit

My daughter is 2.5 and learned to swim last year. She obviously needs supervision but she can float and doggy paddle.

She spent the weekend with her grandmother last weekend who is a firm believer in water wing's and float toy's. We told her that they teach kid's to go vertical on the drowning position so please don't use them. Hold onto her in the pool and let her swim. She agreed.

Well this week we went to swim with her and she seems to have forgotten everything and her grandmother admitted that she didn't like the way she was swimming so she put her in floaties and water wing's. This was over a week ago since she had them.

We tried to get her to swim again but she is screaming for her "muscles" and "donut". She refuses to swim. How long will this last?