If the only posts that Alice makes is "Nice Post", and she is hitting every post on the new tab with that comment, I'd say she is spamming.
OTOH, it is possible that Alice liked the post, and just couldn't find anything to write past that simple sentence...
so in the interest of helping Alice with her next comment, and hoping jerks like me don't flag her back to the Flintstones, I offer:
How to comment on a post past "Great Post!"
In fact, I will add that to the main post in the hope it can help new Steemers who want to contribute