Since I became interested in St. Philomena, about six or seven years ago, I have heard and seen many "statements" that are, in fact, either simply untrue or just plain rubbish. Rather than go through the whole controversy here I refer anyone interested to the excellent article and discussion on Wikipedia: http://en.wikipedia.org/wiki/Philomena.
For me the proof that Philomena both exists and can be honoured as a saint is simply that she was canonised. Contrary to the comments of some (including priests) a canonised saint cannot be "removed" as though he/she had not been canonised or as though the canonisation was a mistake. Canonisation is never revoked even when historical evidence is found wanting. In any case, the problems concerning Philomena date back around a hundred years and there has been more research since then, and she has many devotees in different parts of the world. The official line, sought a few years ago by the authorities at Ars, is that we are free to have a private devotion to her even though there is, strictly speaking, no public cult. Public Masses and devotions in her honour are permitted at Mugnano - the official shrine, and at Ars where the Basilica was built partly in her honour and which houses a special chapel dedicated to her.
Those who become interested in this saint often testify to experiences which have no natural explanation. I give one example here. I know about it because I was personally involved. It concerns a young family. There were twin sons (then aged about 11 I think) and an infant girl. The little girl had an incurable condition which often leads to painful death. Shortly before she died, the parents were praying for the little girl when they heard loud knocking coming from upstairs (or so it seemed). The father of the child rushed up the stairs to remonstrate with the two boys since he assumed they were the cause of the racket. It turned out that they were not involved. St. Philomena is said to knock (often three times) when she is asked for prayers. The child was taken to hospital where the consultant admitted (later) that he was deeply concerned because of the effect approaching death often had on the sufferer in these cases. He was amazed that the little girl died in great peace, with a smile on her face just after she had reached out for her mother's hand. He said he had never seen this happen before in cases like this.
Here is another story which has a natural explanation but contains a strange coincidence (are there coincidences or God-incidencies?). It happened when I was celebrating the Mass. It was after Holy Communion. For some reason I began to think about St. Philomena and my own devotion to her, and wondered why I had never heard the "knocks". Just then came three LOUD knocks. I was amazed. I found out afterwards that a new postman had come to the Presbytery and for some unexplained reason had bypassed the letter-box and come to knock on the door of the sacristy corridor. This had never happened before and it never happened again.
There are more interesting and convincing stories than this but I thought these two might give pause for thought.