Short answer. No. Article 923 lets you take your disinherited parent's place and keep her legitime rights, but it expressly denies your parent any usufruct or administration over that property once it passes to you. She keeps neither the use and enjoyment of it nor the power to manage it on your behalf.
What the law says
but the disinherited parent shall not have the usufruct or administration of the property which constitutes the legitime
Civil Code, Article 923 — The Disinherited Heir's Children Take His Place. Read the full provision →
Your inheritance is not cancelled by her disinheritance
Article 923 provides that the children and descendants of the disinherited person take his or her place and preserve the rights of a compulsory heir with respect to the legitime. So when your grandfather validly disinherits your parent, that disinheritance does not simply eliminate that branch of the family from the estate — you step into your parent's position and remain entitled to the legitime she would otherwise have received. Her disinheritance costs her the inheritance; it does not cost you yours.
But she is expressly cut out of the benefit
The same article closes an obvious loophole immediately after granting you that right: the disinherited parent shall not have the usufruct or administration of the property that constitutes the legitime. Usufruct is the right to use property and collect its fruits or income; administration is the power to manage it. Both are denied to her by name. So while the property passes to you as if you were stepping into her shoes, she does not get to stand behind you and control or benefit from what is, on paper, now yours.
Why the law draws this specific line
Without this second half of the article, disinheritance could become largely symbolic in practice. A parent could be formally cut off as an heir and yet still end up managing the very property her children received through representation — collecting its income, deciding how it is used, effectively enjoying the benefit the disinheritance was meant to deny her. Barring the usufruct and administration closes that gap: the disinherited parent loses not just the label of heir, but any practical hold over the property that passed to her children in her place.
What the article does not settle
Article 923 tells you who is barred from the usufruct and administration — your disinherited parent — but it does not, in this text, say who exercises those functions instead while you are a minor or otherwise unable to manage the property yourself. That is a separate question from what this provision resolves. What the article does settle plainly is that whatever arrangement applies, it cannot be your disinherited parent standing in that role over the property that makes up her own forfeited legitime.