Nothing causes parental guilt to kick in faster than a little one pleading to stay home with you. Even so, if you're sure that your preschooler isn't ill, continue with her normal morning routine. If she protests, tell her, "You need to go to daycare today, but if you're not feeling well we should make sure you get to bed early tonight." Chances are, she'll come around pretty quickly once she hears that.
Your preschooler craves your attention, and separations can be hard for her. Instead of trying to avoid preschool, she probably just wants to spend the day with you. Playing hooky isn't always feasible, of course, and you don't want your child to believe that she can get out of preschool whenever she wants. Still, think about whether the two of you are spending enough time together. Would getting up a little earlier so you have time to snuggle together, read a book, or play a game help her feel better?
Another reason for your preschooler's plea to stay home could be that she's overscheduled. Although she may not actually be sick, she could be so tired that she feels that way. We all have mornings when we'd prefer to stay in bed, of course. But if this "morning sickness" happens frequently, try scaling back her schedule so she has more downtime. Cut back on playdates and other activities, and move her bedtime up a bit to help her squeeze in more rest. You may find that this results in fewer requests to stay home.
Also investigate whether something going on at preschool is bothering your child. Perhaps a move into the "big kids'" class has her feeling insecure, or maybe a favorite playmate is suddenly shunning her. To get to the root of the problem, ask open-ended questions such as "What are you working on in preschool this week?" or "How's your friend Marie doing?"
Make sure to check in with her teachers, too. They should have a pretty good idea of what's causing the problem and what to do about it. Perhaps they'll suggest bringing your child in a few minutes before the other kids arrive, to make the setting seem less overwhelming and to give her a chance to ease in without other kids vying for her teacher's attention. Or they might try to pair up your preschooler with a new friend by making them partners during activities and seating them together during snack or circle time. (You can help solidify the friendship by inviting this new pal over for occasional playdates.) With an ally, your child should feel more comfortable away from home and is less likely to say she's sick when she's not.