What is the meaning of Ellas?

they

Pre-reform spelling (used until 1943 in Brazil and 1911 in Portugal) of elas.

they f

they, them (used subjectively and after prepositions; can refer to women and feminine nouns)

Not used with con; conmigo, contigo, and consigo are used instead, respectively

Like other masculine Spanish words, masculine Spanish pronouns can be used when the gender of the subject is unknown or when the subject is plural and of mixed gender.

Treated as if it were third-person for purposes of conjugation and reflexivity

If le or les precedes lo, la, los, or las in a clause, it is replaced with se (e.g., Se lo dije instead of Le lo dije)

Depending on the implicit gender of the object being referred to

Used primarily in Spain

Used only in rare circumstances

Source: wiktionary.org