Considering as blank any space between the words, the correct is the following:
When their little girl turned five, her parents threw a huge birthday party. They invited all the little girls in the neighborhood. The girls had fancy makeovers, they watched a circus with actual tigers and acrobats, and they ate a gigantic five-tier strawberry cake.
Explanation:
<u>Dependent clauses are separated by a comma. </u>
<em>When their little girl turned five, her parents threw a huge birthday party.</em>
<u>When listing more than two items, you separate them all with comma, even if you use the word "and".</u>
<em>The girls had fancy makeovers, they watched a circus with actual tigers and acrobats, and they ate a gigantic five-tier strawberry cake.</em>
