[quote="FirstCalled, post:1, topic:241608"]
My sister is considering a divorce. In our eyes she will still be married. However my mother says that the Church does not recognize civil marriages, and says that an annulment would not be necessary. I think that the marriage sacrament is between the two people and not done by a priest. So would she need an annulment?
No one here can make a determination regarding the validity of a specific marriage. We can suggest that your sister go talk to a priest.
You have left out many details including the baptismal status of both parties, whether or not canon law requirements were followed if one or both were Catholics, any prior bonds or impediments, etc.
Here are some generalities regarding marriage:
*]The Church recognizes as valid a marriage between two non-Catholics who are otherwise free to marry (no prior marriage or other impediments) regardless of whether they exchange vows in a religious ceremony or before civil authorities. If both parties are baptized, the marriage is valid and a sacrament. If one or neither are baptized, the marriage is valid and a natural marriage.
*]The Church recognizes as valid those marriages between Catholics, or between a Catholic and a non-Catholic, where canon law is followed including all necessary premarital paperwork, determination of freedom to marry, and any dispensations or permissions needed regarding the marriage.
*]The Church recognizes as invalid marriages involving a Catholic or Catholics when the Catholic party did not follow canon law and obtain required permissions and dispensations. In some countries (such as the US) Catholics who were in an invalid marriage due to marrying outside the Church (called 'lack of form') must complete a paperwork process with their diocese to be declared free to marry. So, while there is no decree of nullity, there is paperwork.