I have to respectfully disagree a bit with Slarti - I can see where "begging" for reviews from supporters would be popular and common practice for ambitious authors, but I don't think that necessarily makes it good etiquette.
I just got back from a seminar about marketing and publishing books. Based on what I was told by the instructor (who has 40 yrs experience in the business) combined with what I have learned on ehell, I will say the following:
Asking people to read your book and either a) give you constructive honest feedback and/or b) tell other people about it - that is okay. IMHO, you should not tell them to buy
your book, that is pushy and crass. You can however tell them all the myriad ways they can find
your book. I compare it to the "push vs pull" described when discussing gift etiquette. Telling anyone, family or strangers essentially "hey, drop money on my [book/play/movie/art etc.]" is not appropriate. You could, however, do something like invite them to a publishing party and let them know that *ahem* your book will be available for sale at said party. So you can sell your book, but you need to sell it the right way to the right people. I would not say spamming your list of FB "friends" ranks very high in sales methods, especially if worded incorrectly.
That being said, I think her greatest error was not asking you to buy it, but asking you to REVIEW it. The rule used to be that authors do not ask for reviews. This used to be mostly referring to them contacting professional book reviewers (that's what an agent/publicist is for), but since the advent of self-publishing/Print On Demand etc. and places like Amazon I think it needs to be amended. IMHO, asking for reviews, especially asking for good
(possibly undeserved and automatically biased) reviews is tacky...and asking for good reviews for the express purpose of boosting your book sales is horribly unethical!
You can ask people to read it and possibly review it, but you can not expect them to (unless it is their job like Yvaine above me and even so this means they are very busy reading other things!
), and you are not owed or guaranteed a good review. I wouldn't care if my brother gave my book a 4 star review...I want the total stranger who has no personal stake whatsoever in the book and no feeling towards me as a person to give me a 4 star review. Then I don't have to worry about things being awkward between us.
Getting public reviews (as opposed to private feedback) from people you know is quite the double edged sword!!
So OP, you may read it or not depending on your preference, but IMHO you should feel no obligation to review it, and you are right to worry that reviewing it honestly (and negatively) could impact your relationship
with this person.
PS: The OP's scenario is one reason why I take all Amazon reviews with a huge
grain of salt.