Read the last ten pages and call it done. Did you say specifically that you would read the WHOLE book?
If she really is a friend and you don't want to ruffle her feathers, I would lie and say that even though romance novels usually aren't your thing that you really enjoyed her book and that you think it's terrific that she's been published (unless it was self-published) and that you wish her well for future novels.
Not saying that's what you should do, but that's what I would do if it was a friend.
Jo...telling white lies since the 1960s.