Yes, that's correct! When your friend says she is turning 25 and it will be her 25th rotation around the Sun, she is referring to her 25th birthday. The term "rotation around the Sun" refers to one complete orbit or revolution a planet (including Earth) makes around the Sun. In this case, it means that your friend has experienced 25 full years since the day she was born, and each year corresponds to one complete orbit of Earth around the Sun.