I don't understand what Rosalind is trying to get at in her speech ''And why I pray? Who might be your mother.......'' I'm trying to get into an acting school and I'm practising for next year. I don't understand is she going through a range of emotions, like at the start is she scolding then she goes on to be complementary and then scornful. Is there any humor in it? I'm not criticising just wondering.
I would take advantage of the humor of the situation. If you are having trouble with a character's motivation, it is helpful to be sure to read the play or at least the summaries. A site like enotes will be very helpful for this purpose, as you can read the character analysis.
It's actually quite humorous because Rosalind is taking Phoebe down several notches for being such a vain, prideful woman. But she's not only scolding Phoebe - she's also scolding Silvius for worshipping Phoebe like some kind of a goddess. Rosalind even says,
'Tis not her glass, but you, that flatters her,
And out of you she sees herself more proper
Than any of her lineaments can show her. (3.5)
She's telling Silvius that Phoebe doesn't even have to look into a mirror (her glass) to see how wonderful she is - Silvius does it all for her, thus making her even more prideful and contemptuous of a person.
Unfortunately, this all backfires on Rosalind (who is, of course, disguised as a boy at this point) because Phoebe decides she's in love with Rosalind (Gannymede), who is a stronger "man" than Silvius.
Have you watched the Branagh version of this film yet, with Bryce Dallas Howard as Rosalind? I highly recommend it - She does a great job of bringing this vibrant character to life! Good luck!
compare the characters of celia and rosalind in 200 words