1) Plot is in your mother's name,
2) Your mother can gift it to anyone out of natural love and affection.. The Gift Deed has to be properly executed.
This is how it seems from the case as presented by you. Rest would depend upon counter claims, facts and evidences etc.
DISCLAIMER : General information and advice provided is without any warranties as to suitability for any use, correctness and application to any specific case. Please always take proper legal counsel . However, if it helped anyone even a little a " thanks" would be appreciated and would encourage me to keep on making efforts :-) . I am also always open to corrections and further learnings from more experienced Seniors here.