Hi
Technically, your marriage with the girl is null and void , given that the girl's first marriage was subsisting when she got married to you.
However, it is mandatory that you apply to the family court under section 11 of Hindu Marriage Act and get your marriage annulled on the grounds that the marriage is null and void.
You can get married after you obtain an annulment decree from the family court.
The girl can file false cases under 498a, domestic violence act etc, however you can win these cases on the grounds that the girl was leading illegal marital life with you.
Hence no worries.