Chixdilla, a friend of mine always deliberately worked a teeny tiny error in every project, even those given as a gift. She felt it truly made each item one of a kind. That said, I agree your cousin will adore the blanket, as filled with love as it already is.
And you may find that a distraction project, like that dishcloth, worked on when the blanket drives you bonkers may be enough to let you go back to the blanket with a fresh mind... working something I don't have to think that much about is my favorite way to get through a challenging new technique or project.
Good luck and happy knitting!
"Knit on, with confidence and hope, through all crises."
- Elizabeth Zimmermann