Elle and on are both subject pronouns. They are not used together in the manner you described in your question.
It seems like you are conjugating the verb "avoir" (to have). In this case, you would be writing "elle/on a", which means "she/one has".
If you mean 'elle' as in French, it is hi.
elle s'assoit mean she sits or she's sitting.
Elle a faim means "She is hungry".
elle l'aime means she loves him (or her) in French.
"Elle porte" means: She wears. or She carries.
she/her
she = elle
Elle est gayShe is gay. (lesbian)
elle adore lire - she loves reading
she likes/she loves is translated "elle aime" in French
Where was he(il)/she(elle) born?
Elle s'appelle comment means What is her name?