Personally, I don’t feel so. If gods can be questioned, why not Mahatma Gandhi, who was a human after all, with copious human follies? Of course you can say of all people how come Mayawati speaks from a moral high ground? After all she’s an opportunistic, corrupt politicians who has done zilch for the Dalits aside from providing them vicarious pleasures by wallowing in obscene and hedonistic opulence and indulging in toothless saber-rattling.
Nonetheless, the Congress doesn’t have copyright over the name Mahatma and doesn’t automatically become the aggrieved party if somebody criticizes him. So she should specially not apologize just because the Congress has demanded the apology.