All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.
Standing up straight after raising from Rukoo’ (bowing) and observing the Tuma’neenah while standing up from Rukoo’ is one of the pillars of the prayer without which the prayer is void. Tuma’neenah is the tranquility in all the positions of the prayer. The limit of Tuma’neenah is that each body part settles in its place for the least time possible (before one moves from one position to another). So if this is achieved, then the obligation is fulfilled. It is not obligatory to continue for more time beyond what is obligatory, but what exceeds the obligatory Tuma’neenah is recommended.
The author of Al-Insaaf – one of the Hanbali books – said regarding the adopted view of Hanbalis regarding Tuma’neenah, “The minimum of it is that one observes tranquility/stillness even if this is for a short period.”
Hanafi scholars did not make it obligatory to observe the Tuma’neenah when rising from Rukoo’, rather, they consider doing so as only recommended.
The author of Al-Furoo’ said, “According to the Hanafi School, the Tuma’neenah in other than Rukoo’ and Sujood (prostration), and in them, is recommended, and it was also said that it is an obligation and that if one does not do it out of forgetfulness, he must prostrate for forgetfulness.”
Therefore, if your relative fulfills the obligatory extent of Tuma’neenah, as it appears, then her prayer is valid – Allah willing. If she does not fulfill this extent of Tuma’neenah, then, according to the view of the majority of the scholars, her prayer is invalid.
As regards Takfeer (considering her a disbeliever), then there is no doubt that this has nothing to do with the issue in question. Declaring someone to be a disbeliever is a very serious matter, so you should be very careful in engaging in this devastating issue. Please refer to fatwas 8106and 87963.
With regard to advising her, then this should be done in a gentle and soft manner while clarifying the evidence regarding fulfilling the Tuma’neenah, such as mentioning the hadeeth of the man who did not perform the prayer correctly, after which the Prophet ordered him to repeat it, as well as other evidence that stipulates that the Tuma’neenah is one of the pillars of the prayer.
For more benefit, please refer to fatwas 200531 and 180233.
Allah knows best.