This is the 13834th most frequent Spanish word.
serle
"Serle" means "to be to/for him/her/it" in English, used to indicate something attributed or relevant to someone/something.
In this sentence, 'serle' is used as an indirect construction meaning 'to be useful to someone', where 'le' refers to 'her friends'.
Ella siempre trata de serle útil a sus amigos.
She always tries to be useful to her friends.
Here, 'serle' signifies 'to be something to someone', and 'le' acts as the indirect object denoting 'to others'.
Es importante serle respetuoso a los demás.
It is important to be respectful to others.
In this case, 'serle' expresses 'to be loyal or faithful to someone or something', and 'le' links the verb to 'your own convictions'.