Ideas to protect tiny plants from the frost

Hi there! my mother is an avid gardener and with spring coming up, she's about to make it her whole thing. Where we live, May often has at least a few random snaps of cold and morning freezes that would kill her plants. Usually she'll go out (often in bad weather) and individually put a plastic cup with a rock on it on each and every one of her plants, and there's at least 50. Take them off the next morning. Rinse and repeat.

Does anyone know of any other methods that help protect individual plants from frost? From what I can find, those tent things are only for shrubs and tiny trees. Her birthday is coming up and I'd love to get her something that would make her life easier!