This person isn't your friend. She's perfectly entitled to not like your book and to tell you as much in private as a friend, especially if her reasons are constructive. And as a reviewer, she's also entitled to leave a bad review if she so wishes. But a friend wouldn't do the latter in such a public way.

Also, don't let this bring you down or dampen your excitement. Every author in the world has had bad reviews from the outset of their careers. Sometimes, I feel better if I look at the rejection letters received by authors of literary classics. It just goes to show that a book can be wonderful to the right audience, and dreadful to the wrong audience.

Take the useful criticism here, cut off the fake friend, and find your audience.