Is it truly mandatory that she go? Do you stay home or can you make arrangements for her to spend her days elsewhere (grandma's house, a favorite aunt, etc.)?
In PA, the compulsory school age does not start until 8 (I don't know if you're in PA, though). Most states, it's 6. So if she's only 5, maybe give her another year.
I imagine she's seen that school is, in fact, NO fun at all. Lying & telling her it's going to be SO much fun I think causes more harm than good b/c the truth is that school sucks on too many levels to mention. Having to ask when to pee, being in trouble for talking when an idea hits, marching in a straight, quiet line, often getting in trouble for things that seem extremely random, etc. Going from the freedom to follow your own body's desires (bathroom when needed, eating or drinking when needed) to having to ask permission and being denied until it's more convenient for someone else is NOT fun. It's also not mandatory in order to achieve a decent life - many, many people are waking up to this fact and are homeschooling or, in my opinion, better yet, unschooling. I'd encourage you to respect your daughter by having a dialogue about why she suddenly dislikes school, offering to help her with whatever she identifies and, if that doesn't help, consider pulling her out until next year (or until never again!). School isn't for everyone regardless of how much the system tries to crush out the individual to create a mindless follower.