The time that Sima You Yue had spent practicing Spirit Skills was not long because the book said that any ranks below Spirit King were not able to practice them. As a result, she waited until she was a Spirit King before she started practicing.
Furthermore, the time she spent rising from Spirit King rank to Spirit Overlord was not that long.
Although the time wasn't long, she was still considered pretty skillful. The way she executed the moves was natural and elegant, causing others to be starstruck. If the people from the Sima Clan saw it, they would definitely be beside themselves in shock.