A: While we are always cautious to avoid any kind of rigid dogma when it comes to discussing angelic beings and the divine order of the universe, we must point out that the holy books of the great world religions agree that angels are an earlier and a separate order of creation from human beings. Therefore, a human does not die and become an angel. We were created a "little lower than the angels," and we join them in the heavenly realm as distinctly human personalities and energy forms.
The teachings of Islam state that there are three distinct species of intelligent beings in the universe. The first are the angels (malak), a high order of beings created of light; second, the al-jinn, ethereal, perhaps even multidimensional entities; and then humans, fashioned of the stuff of earth and born into physical bodies.
For hundreds of years, some books and plays have depicted the spirit of a deceased individual sprouting wings and rising to heaven--literally becoming an angel at the moment of death. Often in various productions, such as "Uncle Tom's Cabin," the actor was outfitted in a pair of wings and hoisted by means of rope and pulley to soar above the scenery to accentuate the portrayal of an ascension to a higher dimension.
Although we humans do not become angels, we have every reason to believe that we are special entities with important earthly responsibilities and missions. So special are we that, according to some traditions, certain of the angels are jealous of our human attributes--especially our free will--and resent the attention that the Supreme Being shows toward our spiritual evolution.
So while, in the strictest definition of the title we do not become angels when we die, there are at least two possible responses to those who feel that a deceased loved one has become their guardian angel. First, souls may temporarily be held earthbound by the grief of their families and appear to assume the role of a guiding presence.
Second, angelic beings, in order to effect more immediate communication, may assume the appearance of a deceased loved one. But these are simply our thoughts. We are not dogmatic nor do we seek to impose our human understanding on others with regard to the limits of God's creative powers.