The reality of an apparition of the Virgin Mary doesn't affect the dogma of faith by which the faithful are bound.
Everyone knows that the Mother of God can appear and help her children: the practical question is, then, to determine whether one can seriously believe that she did appear here or there, in places where some people say they have witnessed extraordinary phenomena.
In any case, the judgment of the Church in such matters isn't concerned with the divinely revealed faith; it is rather a pastoral pronouncement, for the good of the faithful, with a varying degree of certainty.
The Church doesn't for herself claim infallibility in those areas, and even when she does make a firm pronouncement, saying that the reasons for believing in an apparition are strong, each individual remains free in his own conscience to believe in it or not.
Amidst the approved sanctuaries and the places explicitly condemned by the ecclesiastic authorities, there still remain a number of sites whose status is less clear.
Among them are quite a few ancient shrines where popular devotion has established its uncontested grounds, without incurring the official judgment of the Church.
More importantly, you will find a great number of recent sanctuaries that are attracting crowds and producing fruits whose soundness only time will tell.
Faced with this recent multiplicity of claimed apparitions it is sometimes difficult to decide on what to believe. Mary is a mother who calls us, and all the authentic, approved apparitions, were once non-endorsed places of pilgrimage. At the same time we mustn't lend ourselves to grotesque or unrestrained credulity or a taste for the sensational which doesn't correspond to what Jesus expects of us.
In these and other matters, if we have been attracted to one supernatural account or another, because it looked beautiful and powerful to us, we should solicit the opinion of holy priests.
Above all, it is essential to maintain a sense of humility and obedience in these matters that are beyond our grasp, if we don't want to be misled. Let's not forget that our goal is to imitate the humble handmaid of the Lord!