Is it a valid Christian concept to attribute subjectively attactive physical characteristics, as blessings from God? In conversation with a fellow Christian the other day, she used the phrase, "God has blessed her with very attractive looks" describing a mutual friend of ours (about whom I agree on the attractive aspect).

If someone is considered very attractive (to narrow that word down - opinion held by the majority, subjectively within a culture, that the person is good looking) is it correct to automatically classify this as a blessing from God?

A few reasons this question comes up is because what does that mean for another female who is at the lower end of that spectrum, where it causes her much pain in her life - from finding a mate to how self-esteem carves her reality? Would that be considered a lack of blessing, of the enemy, or simply chance of the physical world? Or, does it have nothing to do with blessings and is more like a slang Christian phrase?
Yes, it is completely valid to attribute any blessing to God from a variety of Christian perspectives. In short, all things are ordained by God.

As for the "less attractive" person, God has most likely blessed her with other attributes.

And if not, a perfectly Christian answer to why some are blessed with certain things and other are not is the one God gave to Job... "Where were you when I laid the foundations of the earth?". In other words, who are we to question God?  Rather, according to most Christian teachings, we should thank God for what we have, realize that all blessings come from Him,  and not complain about what we didn't get.