What are the signs of fall in your own home? Observe with her and brainstorm: thicker blankets on the bed, decorations change on the wall, shopping for school clothes, trying on last year's winter coat to see if it will fit, switching to heat instead of AC. As someone else suggested, walk outside and look. The idea is to teach them to observe and report on it, not to have the most imaginative thing. Also, after everyone brings stuff in, they usually use the same topic for math: how many leaves were brought, how many halloween candies, making charts and beginning to think about fractions (half the class brought leaves), etc. My kids did the same, and it is also about becoming comfortable speaking up in class. In 1st grade the show and tell was during snack time, so all they had to do was stand up and say 1 or 2 sentences about their thing and then 3 kids could each ask 1 question as chosen by the presenter. Make it fun, and let her choose.