I just fed your information into the [Steve Morse's Relationship Calculator][1] in this order:

 1. parent
 2. sister
 3. husband
 4. daughter
 5. daughter

and it returned that your parent's sister's husband's daughter's daughter is to you a 

> ???  (non-blood relative)

If you ignore the "husband" that led to the step then you get (as @TomH said)

> 1st cousin once removed  (blood relative)

If you really want a label for the non-blood relationship between you, then I think the following would be as good as any:

> step 1st cousins once removed

[1]: http://stevemorse.org/relation/calculator.html