Hi Taylor!
I believe that harm is all of the above- mental, physical, and emotional. In my view, one should not harm without purpose in any of those forms. I think in the example you gave, writing a bad review could be seen as harmful, but it has a purpose. I think that random unnecessary harm is where his principle is useful. To Mill, in my view, harm is anything that may infringe on someone elses liberty. This can be a broad range as well, but I do not think he would see writing a bad review as harm, because it is a liberty we have of free speech, and really does not violate the other's liberty either.
And for abortion, I see how you can respectfully disagree, however, a woman has a choice to avoid the mental, emotional, and or physical trauma that comes along with birth especially under certain circumstances.