Too much "X" chromosome

[Tasha]

Through commercial DNA testing, I found that this lady is my 1st cousin once removed or my second cousin,  We share 356.3 cm and the longest segment is 44.99.

Her mother and my father's biological mother were sisters.

Odd thing is I share 90.1 cm of "X" chromosome with her.  More than I do my maternal half sister.

I do not know who my father's biological father was as of yet.

I sent my DNA to a geneticist/genealogist who believes that my father's parents or grandparents may be closely related. 

So I am searching for an explanation as to why I share so much "X" with my father's maternal cousin.

 

Tasha