What is the ruling on tayammum in a mosque when water is available for a woman who went out shopping at noon, and her intention was to quickly attend to her needs?

The prayer of the woman mentioned is invalid and must be repeated if she prayed with tayammum while water was available and she was able to use it. She must perform ablution in the area designated for women or in the bathroom while covering herself, for tayammum is only permissible when water is absent or one is unable to use it.