Umesh - she can sell the property but she needs to deal with the restriction. Probate is not required as the legal ownership passed to her on his death and did not form part of his estate.
If she is now the sole legal and beneficial owner she can cancel the restriction -
see PG 6 section 7 or
She can transfer it by following the guidance in
PG 21 section 6
The second option is 'quicker' as part of the selling/buying process and not a separate application