Hurt With A Lie

Today...my friend was received a call from his sister...
and his sister told him something...and lie him...
This is straightly HURT to my friend and feel speechless after he knew that ALL his sister told him may A LIE..
my friend told me that He hopes the all lie from his sister is fake...
i hope so...because i don't want to see both of their relationship become worst...
My friend scare to ask his sister whether it is true or not...
He worry the answer by his sister....HE FEELS NERVOUS...!
What can he do now? What should he do? How??Why his sister wanna tell him A LIE?
i also don't know how to help him...Im just guessing now...whether my friend's sister got tell him A LIE or not...but i think that his sister is lying my friend... don't know...Whatever i think is useless....
Well...........
Everything can proven by the time ... I'm sure that there is an answer waiting for him...