In Act I, scene III, we meet Celia and Rosalind. Rosalind's father has been banished by Duke Frederick (Celia's father), but Rosalind herself has been saved because she and Celia love each other more than true sisters:
The other is daughter to the banish'd duke,
And here detain'd by her usurping uncle,
To keep his daughter company; whose loves
Are dearer than the natural bond of sisters. (I.ii.290-293)
The women learn of a wrestling match that will take place at Celia's house, on the lawn, and the women attend. There they meet Orlando and try to keep him from wrestling, for they fear for his safety and/or life. He says that there is no one in the world that would miss him, but he appreciates their concern. He fights Charles and beats him. Afterward, feeling connected to Orlando in that his sense of isolation is similar to her own, Rosalind gives him her necklace to wear, for she has little else to offer him in her reduced circumstances.
[Giving him a chain from her neck.]
Wear this for me; one out of suits with fortune,
That could give more, but that her hand lacks means.--
The women leave. This ends Act One, scene two. At the beginning of scene three, Celia says to Rosalind:
Why, cousin; why, Rosalind;--Cupid have mercy!--Not a word?
In this line, Celia is asking Rosalind if she has nothing to say, or why she is so quiet.
In the ensuing conversation, we learn that Rosalind (daughter of Duke Senior) has a great deal on her mind, such as her father's predicament and her own because of her father's banishment, and now she is also preoccupied by her increasing thoughts Orlando, something which Celia asks Rosalind about.
...let us talk in
good earnest: is it possible, on such a sudden, you
into so strong a liking with old Sir Rowland's youngest
It is here, for the first time, that we learn that Orlando has been much on Rosalind's mind, and that her feelings for him are growing.