Whoever told her that is absolutely incorrect. She should make an appointment to speak with her priest or deacon or someone who handles annulment at the archdiocese. There are also usually seminars set up once or twice a year in most areas. My recommendation would be to find a procurator to work directly with her. This may be a deacon in the parish or a lay person.
There is no guarantee that an annulment is granted, but if the only reason she has not pursued it was because of the existence of children, then she was misinformed and should speak with someone directly involved in the process.
An internet search can give lots of information about potential reasons why a marriage might be null, but the best advice will come from whomever she chooses as a guide. Annulment is not quick, and it is not easy, but it is worth the effort.
Love,
O2
See this is the problem; an annulment being difficult to obtain when the evidence of adultery and abandonment are clearly established is a poor emulation of Christ’s commands. This bureaucratic process pins the victim down despite the simple Truth of Christ thus the frustration level reaches the point of, in my sister-in-laws case, to leave for another Church. The Church needs to seriously fix the red tape. One simple conversation and a copy of the divorce decree stating the reasons (Which in Florida you do) should be enough. This is probably one reason why Pope Francis is getting looser with the Communion restrictions, however the fix should pertain to the bureaucracy.