There are several aspects of marriage that may affect Social Security benefits. It's best to seek individual counseling on this.
For example, depending on her age and previous marital status, she may be eligible for survivor benefits from a previous marriage that may "disappear" upon remarriage. In general, you cannot receive survivors benefits if you remarry before the age of 60 unless the latter marriage ends, whether by death, divorce, or annulment.
As far as your retirement benefits, if a husband and wife retire, each receives his or her own benefit amount. Social Security imposes no "marriage penalty" when two members of a couple are each entitled on their own earnings record.
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