In Romeo and Juliet, when Juliet is left alone with her mother and then the Nurse, how do their responses differ?

I am going to assume, since you do not specify, that you
are referring to Act III, scene v, just after Lord Capulet has exploded because Juliet
refuses to marry Paris.  He basically tells her to marry Paris or he'll kick her out to
"Beg!  Starve!  Die in the streets!"

When he exits, the
first person that Juliet appeals to is her mother, but she finds little comfort here. 
Lady Capulet says:

readability="9">

Talk not to me, for I'll not speak a
word.

Do as thou wilt, for I have done with
thee.

So, she basically
washes her hands of the situation, even though it might mean her daughter turned out
into the streets with nowhere to go and no way to support herself.  She either doesn't
care what happens, or is not willing to cross her husband in support of Juliet.  Either
way, she has no kind words for her daughter.

The Nurse,
gives Juliet the advice to marry Paris.  She tries to pretty up the suggestion by
talking about how much better a catch Paris is than Romeo.  She also thinks Juliet will
be better off.  She says:

readability="23">

. . .Beshrew my very
heart,

I think you are happy in this second
match,

For it excels your first; or, if it did
not,

Your first is dead, or 'twere as good he
were

As living here and you no use of
him.

Juliet

Speakest
thou from thy
heart?

Nurse

And
from my soul too, else beshrew them
both.

And so it appears she
does speak from her heart.  Though Juliet does not follow the Nurse's advice, it seems
to be spoken from deep love and care.  She certainly, unlike Lady Capulet, takes the
time to do her best to counsel and comfort Juliet, behaving more like a mother to Juliet
than her own mother does.