Apart from any moral dilemas, which are a matter for the parties concerned - sexual intercourse with a minor is a criminal offence, and the lady in question could face criminal charges if this activity were discovered. From a relationship point of view, you would have to question the approach of a mature woman who would wish to embark on a relationship with someone legally considered a child, how ever mature the child's outlook may appear, and the potential damage to both individuals should their liason become public knowledge. So, legally, yes it is wrong, morally, it's your call.