For Shakespeare's Twelfth Night, I need to write about how Maria makes a mockery of love.* I already wrote about her thinking that love is shallow...

You might want to look at Act I scene v, when Viola enters (as
Cesario) into Olivia's presence.  Some of the mockery here is a bit inferred and indicated by
action rather than text, but I believe that this scene could also be
useful.

Just before Viola enters, Olivia says to
Maria:

Give me my
veil.  Come throw it o'er my face.

Well once again hear Orsino's
embassy.

This line is important when
considering mockery in this scene, since it shows that Olivia has covered her face when receiving
suitors sent from Orsino in the past.  Are they preparing a ruse that they have enacted upon past
emissaries sent from Orsino before?  This idea that they are, once again, creating a ruse, or
playing a trick, can be inferred upon Viola's opening line:

readability="6">

The honourable lady of the house, which is
she?

With this line, Viola exposes
that she is confused by which of the women is which.  Why does she confuse a waiting woman and
her maid? Does Maria also throw a veil over her head to appear to be the same as Olivia?  It is
often played this way in performance.  And if so, doesn't this mean that she is mocking Orsino
and his "love" for Olivia?

Maria has only one line in the scene,
"Will you hoist sail, sir?  Here lies your way."  When Viola answers this with "Some
mollification for your giant, sweet lady!"  She indicates that Maria is either trying to bodily
throw her out, or is at least threatening to do so, and Viola is appealing to Olivia for help. 
Again, an indication that Maria is mocking Orsino and the messenger he
sends.

I tend to agree with you, that it is difficult to find
support for Maria's making a mockery of love.  But looking at the subtlties of certain moments,
as I have above, can give you more support for creating such an agrument.  Good
luck!