" Any person interested in an estate, e.g a person sharing in the estate , or a legatee or a creditor , may call upon the personal representative of the deceased, whether he is an executor or an administrator, to exhibit an inventory of the estate and render an account of his administration thereof " That's a quote from a current, standard book on 'Probate Practice' . (That's been the law since a case reported in 1797, so there's nothing new in it)
If you are to be a beneficiary under the will then you are definitely entitled to such an account.Even if not, as the son or daughter of you late mother, you could surely argue that you are a 'person interested' .