From Dom Guéranger's The Liturgical Year.
The holy virgin who this day claims the homage of our devotion and praise, is offered to us by the Church of Alexandria. Apollonia is a martyr of Christ; her name is celebrated and honoured throughout the whole world; and she comes to us on this ninth day of February, to add her own example to that which we have so recently had from her sister saints, Agatha and Dorothy; like them, she bids us fight courageously for heaven. To her this present life was a thing of little value, and no sooner did she receive God’s inspiration to sacrifice it, than she did what her would-be executioners intended doing: she threw herself into the flames prepared for her. It is no unusual thing, nowadays, for men that are wearied of the trials, or afraid of the humiliations, of this world, to take away their own lives, and prefer suicide to the courageous performance of duty: but Apollonia’s motive for hastening her death by a moment’s anticipation, was to testify her horror of the apostasy that was proposed to her. This is not the only instance we meet with, during times of persecution, of the holy Spirit’s inspiring this lavish sacrifice to saintly virgins, who trembled for their faith or their virtue. It is true, such examples are rare; but they teach us, among other things, that our lives belong to God alone, and that we should be in readiness of mind to give them to Him, when and as He pleases to demand them of us.
There is one very striking circumstance in the martyrdom of St. Apollonia. Her executioners, to punish the boldness wherewith she confessed our Lord Jesus Christ, beat out her teeth. This has suggested to the faithful, when suffering the cruel pain of toothache, to have recourse to St. Apollonia; and their confidence is often rewarded, for God would have us seek the protection of His saints, not only in our spiritual, but even in our bodily sufferings and necessities.
The liturgy thus speaks the praises of our saint.
Apollonia, virgo Alexandrina, sub Decio imperatore, cum ingravescente jam setate ad idola sisteretur, ut eis venerationem adhiberet, illis contemptis, Jesum Christum verum Deum colendum esse prædicabat. Quamobrem omnes ei contusi sunt et evulsi dentes: ac, nisi Christum detestata deos coleret, accenso rogo combusturos vivam minati sunt impii carnifices. Quibus illa, se quamvis mortem pro Jesu Christi fide subituram respondit. Itaquecomprehensa ut combureretur, cum paulisper quasi deliberans quid agendum esset, stetisset, ex illorum manibus elapsa, alacris in ignem sibi paratura, majori Spiritus sancti flamma intus accensa, se injecit. Unde brevi con9umpto corpore, purissimus spiritus in cœlum ad sempiternam martyrii coronam evolavit.
Apollonia was a virgin of Alexandria. In the persecution under the Emperor Decius, when she was far advanced in years, she was brought up to trial, and ordered to pay adoration to idols. She turned from them with contempt, and declared that worship ought to be given to Jesus Christ, the true God. Whereupon, the impious executioners broke and pulled out her teeth; then lighting a pile of wood, they threatened to burn her alive, unless she would hate Christ, and adore their gods. She replied, that she was ready to suffer every kind of death for the faith of Jesus Christ. Upon this, they seized her, intending to do as they said. She stood for a moment, as though hesitating what she should do; then, snatching herself from their hold, she suddenly threw herself into the fire, for there was within her the intenser flame of the Holy Ghost. Her body was soon consumed, and her most pure soul took its flight, and was graced with the everlasting crown of martyrdom.
What energy was thine, Apollonia! Thy persecutors threaten thee with fire; but far from fearing it, thou art impatient for it, as though it were a throne, and thou ambitious to be queen. Thy dread of sin took away the fear of death, nor didst thou wait for man to be thy executioner. This thy courage surprises our cowardice; and yet, the burning pile into which thou didst throw thyself when asked to apostatize, and which was a momentary pain leading thy soul to eternal bliss, was nothing when we compare it with that everlasting fire, to which the sinner condemns himself almost every day of his life. He heeds not the flames of hell, and deems it no madness to purchase them at the price of some vile passing pleasure. And with all this, worldlings can be scandalized at the saints, and call them exaggerated, extravagant, imprudent; because they believed that there is but one thing necessary! Awaken in our hearts, Apollonia, the fear of sin; for sin gnaws eternally the souls of them who die with its guilt upon them. If the fire, which had a charm for thee, seems to us the most frightful of tortures, let us turn our fear of suffering and death into a preservative against sin, which plunges men into that abyss, whence the smoke of their torments shall ascend for ever and ever,as St. John tells us in his Revelation. Have pity on us, most brave and prudent martyr. Pray for sinners. Open their eyes to see the evils that threaten them. Procure for us the fear of God, that so we may merit His mercies, and may begin in good earnest to love Him.
 Apoc. xiv. 11.