Short answer. No, not on that basis alone. The Rules of Court's definition of a legally "incompetent" person who may need a guardian covers deaf and dumb individuals only if they are unable to read and write. Someone who reads and writes fine does not fall under that specific ground, though guardianship could still be sought for another qualifying reason.
What the law says
the word "incompetent" includes persons suffering the penalty of civil interdiction or who are hospitalized lepers, prodigals, deaf and dumb who are unable to read and write, those who are of unsound mind, even though they have lucid intervals, and persons not being of unsound mind, but by reason of age, disease, weak mind, and other similar causes, cannot, without outside aid, take care of themselves and manage their property, becoming thereby an easy prey for deceit and exploitation
Rule 92, Section 2 — Meaning of word "incompetent.". Read the full provision →
What counts as "incompetent" for guardianship purposes
The Rules of Court defines who may be placed under guardianship as an incompetent adult. That definition is a specific list, not a general reference to disability. It includes persons under civil interdiction, hospitalized lepers, prodigals, those of unsound mind, and people who, because of age, disease, or weak mind, cannot take care of themselves or their property without outside help.
Deafness and muteness appear on that list, but only in a narrow form: deaf and dumb who are unable to read and write. The disability alone is not the trigger; the inability to read and write is.
Why literacy is the deciding factor here
If your relative is deaf and mute but reads and writes without difficulty, she does not fit the "deaf and dumb who are unable to read and write" ground in this definition. The rule is written around the practical concern that someone who cannot hear, speak, or read or write may struggle to understand transactions or protect their own property. Someone who can read and write fluently does not have that particular vulnerability, so this specific ground for guardianship does not apply to her.
This rule has been updated where the ward is a minor
One important caveat: this provision of the Rules of Court no longer governs guardianship of minors. A.M. No. 03-02-05-SC, the Rule on Guardianship of Minors, effective May 1, 2003, took over that area, amending the older rules in that respect. Guardianship of incompetents who are not minors, however, continues to be governed by the Rules of Court provision quoted above.
So if your relative is an adult, the definition above is the current, applicable rule. If she is a minor, the 2003 Rule on Guardianship of Minors governs instead, and its own grounds for appointing a guardian would need to be checked separately.
Other grounds could still apply
Being literate rules out only the deaf-and-dumb ground specifically. It does not automatically mean no guardianship could ever be appropriate. The same definition also covers people who, for other reasons such as unsound mind, age, disease, or weak mind, cannot manage their own affairs without outside help. If your relative has some separate condition beyond the hearing and speech disability that leaves her unable to safely manage her own property, that could still support a guardianship petition on a different ground entirely.