1. You can marry her in accordance with Special Marriage Act (SMA) whereunder the marriage should be compulsorily registered.
2. To marry a foreigner in India there is a 30 day residency requirement, which means that either the bride or the groom has to be living in India for at least 30 days prior to applying to the local registry office to get married. For foreigners, this is evidenced by a certificate from the local police station or Copy of C Form or FRRO Registration copy accordingly.
3. You are required to to submit your intention to get married to the registrar of marriages (as per your Jurisdiction District), along with the residence certificate (i.e. proof of residence), certified copies of passports and birth certificates, and two passport sized photographs and few affidavits each.
4. If no objections to the marriage are received within 30 days of the application, a civil ceremony at the registry office can then take place. Three witnesses are required, who have to provide passport sized photographs, as well as identification and proof of address. The marriage certificate is usually issued a couple of weeks after the wedding.
5. All she has to do right now is to come with her original Certificates on a Tourist Visa and post registration of Marriage convert it into "X" Visa.
6. As of September 2012, the Ministry of Home Affairs (MHA) has changed the procedure and is no longer accepting direct applications for Tourist visa extension and conversion. Instead, she will need to apply at her local FRRO/FRO, which in accordance with Section 1 must make a recommendation and forward it to the MHA in Delhi for approval if the matter is outside its delegated powers..