All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
It is not clear to us in the question whether or not this marriage was concluded (had taken place).
If the matter is just an engagement, then your friend can simply invalidate it, if he so wishes; there is no sin in this.
For more benefit, please refer to Fatwa 18857.
If the marriage was concluded, then divorce is permissible, especially if there is a need.
We have already clarified this in Fatwa 61804.
Regarding his doubts that her parents had deceived him, then in principle they are innocent and he is not permitted to think evil of them without evidence. Allah Says (what means): {O you who have believed, avoid much [negative] assumption. Indeed, some assumption is sin. And do not spy or backbite each other. Would.} [Quran 49:12]
For more benefit on the defects about which the suitor must be informed, please refer to Fataawa 124714, 158401, 128182, 224071, 89168, 365911, and 362644.
Allah knows best.