Woman praying with a non mahram man.
. Is a woman’s prayer accepted if she prays with a non-mahram man alone?
A. First of all, you must know that it is totally haram to be alone with a non Mahram. It is a sinful action. However, simply on account of this, your salaah will not be considered as being rejected or invalid. The following explaination from the books of Fiqh will guide you to understand the status of your Salaah.
In the famous book of Islamic Jurisprudence, Al Hidaya it states,
‘If a female stands in the same line with a man, and both of them are in the same salaah, then the male’s salaah will be invalid if he intended to lead her in Salaah. The female’s Salaah will not be invalid in this case. The reason for the invalidation of his Salaah is that he (the male) has violated the teaching of the Prophet (SA), and has gone against his clear order. In this matter, the Prophet (SA) issued a clear order, saying, ‘Place them (the female) behind’. (This is a mashur (famous) hadith which has been recorded by Abdur Razak and Tibrani from Abdullah bin Masood (RA)  ).
This narration shows that a man has been ordered to place the females behind in Salaah when forming the lines. Due to the fact that the man has opposed this law, his Salaah will be invalid. The female referred to, in the above Fiqhi text means a female who has reached the age of puberty. The mas’ala (law) goes further to state that ‘in this case, if the male did not make an intention of leading the female in Salaah, then his Salaah will be valid and her salaah will be invalid. This is due to the fact that for her Salah to be valid, the Imam must include her in the Salaah, by having/making the intention to do so. Since, the male (Imam) did not include her in his Salaah while she followed him, her Salaah will not be valid. As for the male, he performed salaah on his own (by not intending to lead the female), hence, a woman standing close to him will not affect his Salaah in this case.
Al Hidaya continues to state, ‘From the conditions of one’s Salaah to become invalid when a female stands close to/in the same line of the male are:-
1) When both of them are in the same Salaah and the male leads the female.
2) The Salaah should be one which has ruku and Sajda. It should be the normal Salaah which is performed. This means that this law will not be applicable to Janaza Salaah since it does not have ruku and Sajda.
3) The female should be one who has reached the age of puberty.
4) There must be no separation between the male and female.
(Al Hidaya vol. 1 pgs 124-125)
Based on this explaination, you can judge the situation and apply the correct ruling.
And Allah knows best.
Mufti Waseem Khan