यस्याः कृते on whose acount, रामः Rama, वने in the forest, वः पिता your father, न्यस्तदेहश्च forsook his body, सा that, पापा sinful woman, नृशंसा च cruel also, इयम् this (Manthara), तस्याः to her, यथामति as you please, कुरु do.

Here is that sinful, cruel woman on whose account Rama is in the forest and your father has forsaken his body. Do with her as it pleases you.