Dealing firstly with the passage on appeal. They have not granted her a right to appeal except on those grounds stated. It does not sound as if she has been discriminated against. The UKBA would argue that her Human Rights have not been discriminated against because she is still free to make a further application remedying the defects. You could attempt to argue that her rights have been discriminated against but you would need a lawyer to do this for you and I don't really think you have good grounds. It would also take a fairly long time with no guarantee of success.
I would advise you to make a further application for a marriage visa remedying the defects yourself and instructing a solicitor to prepare the application for you for resubmission. This will be the quickest way of getting her visa in my opinion.
In particular there you should remedy the defects by doing the following things:-
1. If she has funds in her account it is much more likely to be accepted by the UKBA that she meets the crtieria to be able to financially support herself during her stay. Either you or her parents could transfer a sum of money in to her account asap so that she can show the UKBA she can cover the costs of her stay.
2. You should ask a solicitor to draft and execute a sponsorship declaration executed by you and your wife explaining the situaiton emphasising that it is a visit only for the purpose of marrigae and you understand that she must return. You should state that you will cover the unforeseen expenses of her stay if any arise and shall provide rent-free accomdoation during her stay (if you will). Bank statements should be referred to and attached.
3. Her parents should also executed a sponsorship declaration again stating that they expect her to return to Iran following marriage and that they shall also cover the costs of unforeseen expenses. Your solicitor will be able to research and tell them where they need to go to have this legalized. Bank statements and copy passports to be attached.
4. Your son and his fiancee must both execute detailed statements confriming that they are to marry here but that she is to return home. They must both state that they are fully aware that it is not an option for her to seek to secure leave to remain here whilst on a marriage visitor's visa and that any attempt to do so would be rejected immediately and viewed as a deception whcih they understand can prejudice any future application she chooses to make. Attach evidence of a return flight ticket to Iran, or booking informatoin.
5. They shoudl submit any correspondence they have which substantiates there planning to marry during the visitor. This can be emails, text messages anything in documentary form between the two which refers to their impending marriage.
Provided she has enough funds in her account to cover the costs of her stay and the above defects are remedied with supporting documentation then she should be granted a visa.
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