1. Do not act in a hurry and let her know that you have come to know about her adulterous activities.
2. Adultery is difficult to prove for which you shall have to collect irrefutable evidence of her said act.
3. If you produced half backed evidence before the Court, you shall not be able to get the desired result and on the other hand she will get the chance to retaliate by filing numbers of cases against you like 498A complaint, DV case, maintenance/compensation etc.
4. Do not snatch her phone at all. Rather try to collect/extract data from her phone if possible through blue tooth.
5. After that allow her to proceed further in her said illegal activities which you can get recorded easily and collect irrefutable evidence to prove her illegal act before the Court.
6. Once evidence of her said act is collected, you can file an annulment petition on the ground that her said physical relationship with her paramour was not informed to you while taking your consent for the said marriage.
7. If the marriage completes one year before your acn collect evidence of her having physical relationship outside her wedlock, you can file a divorce suit also against her.
8. Please note that you shall have to prove her having physical relationship out of her wedlock to get divorce or annulment of marriage decree.