Personal Dilemma

I will never truly understand human beings.  One situation I came across today was someone who purposely with held information from someone that they needed, because they don't like them.  I was told to with hold information from someone today and was really uncomfortable being put in that situation. What do you do? Do you go behind your bosses back and give the information or do you just do as your told?  I just did as I was told but wasn't crazy about doing it. The professional world can be insane and cut throat sometimes. I don't think I would ever do something like that to someone even if I wasn't too fond of the person.  Now, with holding the information wasn't going to give her a step forward in the profession.  She simply with held the information because she didn't like her and wanted her to look like an ass by missing a important meeting. Not even thinking that if it gets out that she asked her for the information and she refused to give it to her, she will be the one looking like an ass in the end.  I really hope she doesn't put the blame on me, because if it comes to it, I may actually say, she told me to "Only send her the information for one meeting and not the other because she is a bitch."