So far as I know, she's never publicly stated whether she knows Sanskrit or not. She hasn't ever published her own original translations of any Sanskrit source, so we have no direct evidence that she understands it. Of course, this is not conclusive. One may know a language without feeling to need to provide their own translations of primary texts. She does cite a lot of Sanskrit texts in her writings, but usually through secondary sources, i.e., previous translations by other people.

I understand that claim that she doesn't understand Sanskrit comes from NS Rajaram, who debated her. But Rajaram is also a polarizing figure and has an agenda of his own, so I don't know how reliable this is.

She also does not speak Persian or Arabic, so her knowledge of Indian history from 1200 AD on comes from translations of these sources.

Her reputation originally came from very strongly promoting the Aryan Invasion theory. More recently, as genetic evidence has shown that most of the European haplogroups in the northwestern part of the subcontinent arrived much earlier, this theory has fallen out of favor. Now the current idea is that Indo-Iranic speakers must have been far fewer in numbers, not enough to leave a strong mark on the Indian population genome. And parts of the Rig Veda are recognized as being much older than their composition in Vedic Sanskrit, so the idea of Rig Vedic culture being brought full-fledged to India has become weaker.

She's changed her tune on that somewhat on these issues, but she also says that she's unable to consider this new evidence since she's not trained in science. That's quite understandable.