According to Jain Tattvārtha principles, you cannot be certain of meeting your mother in heaven as your mother.

In Jainism:

• A soul takes birth according to its karma in one of the gatis.
• Heaven (devaloka) is only a temporary birth for the soul with punya karma.
• Family relations are not permanent; they belong to a specific birth.
• So, if your mother has obtained deva-gati and you also reach there, a meeting may happen only if karmic conditions allow—but not as a guaranteed mother-child relationship.

The deeper Jain view is:

• The soul is eternal.
• Bondage is through karma, not through permanent earthly relationships.
• Therefore, attachment to “my mother in heaven” should be transformed into respectful remembrance, punya, and detachment.

So the simple answer is:

No, Tattvārtha Sutra does not teach that you are निश्चित to meet your mother in heaven as your mother. It depends on karma, and worldly relationships do not remain permanent.