No, Roseola is a more fine rash, it doesn't usually start like sores.

Tan, rashes in children are notoriously hard to diagnose. you could do blood tests to determine whether it is chicken pox, but these are not usually done for two reasons:

1) They are traumatic to the child;
2) As there is no treatment for chicken pox, and the rash, once it develops further, is unmistakable, there is no benefit in checking the blood test. Usually, by the time the result comes back, it is already quite obvious what it is.

Seeing as you say she is so happy, I think you can put your mind at ease. Unwell children usually act unwell. As long as she is happy, she is probably OK. And chicken pox is usually pretty mild in younger children and toddlers. Its the older children (and adults) that it tends to be more difficult in.