a) Why would an immigration officer even speak to you, especially as you are not related to the person refused entry (a friend of your daughter)?
b) 'She made the wrong decision' - why do you say that? Simply because the person was refused entry?
c) 'did not investigate the facts properly' - I expect she did 'investigate the facts' but maybe they weren't to your liking.
d) 'assumed too much' - immigration officers are actually quite experienced. Perhaps she was making the right assumption?
There are normally very good reasons why people are refused entry e.g. criminal record, drugs, likelihood of them outstaying their visa etc. Which category did your daughter's friend fall into?
As has been said already, it's for the person concerned to complain about the refusal, not you, as it really doesn't concern you.