..expands the number of words...

[lokasseyve]

Hi,
Her essay is good but kind of short. It'll be more complete if she expands the number of words at the end of the second paragraph.

I made these sentences. I'm not sure if the underlined part works and sounds natural.
Another expression I think of:
...if she increases some words at the end of the second paragraph.

Thank you so much.

 

[e2efour]

I would not say increase/expand the words, but only their number.

You could also say, for example, if she makes the second paragraph longer.

 

[dojibear]

To me you cannot "expand a number" or "increase words". I would swap those: both of these are common:

increase the number of words in the second paragraph (not "at the end of")
expand the second paragraph

or use the #2 suggestion:

make the second paragraph longer