Fan service in shonen anime is pretty common, and it usually involves women in bathing suits and plot fluff featuring fan-favorite side characters. Shojo fan service is a bit different. Fan service written for a female audience tends to be a bit more subtle. It focuses on eliciting an emotion from the audience. Generally, the intent is to incite swooning.
Source:https://www.cbr.com/shojo-anime-with-fan-service/