What are the repurcussions for marrying an illegal alien?
It’s not illegal to get married, but it’s illegal to stay past the visa expiration. If you get married in the US, it will be a legitimate marriage, though you will need government-issued identification, and all she probably has is a passport with an expired visa. Under normal circumstances you could have applied for a fiancee visa, get her to US and marry her. The fiancee visa may now be denied due to the visa irregularities.