Should the questioner reject a righteous, married man who proposed to her, out of fear of how Egyptian society and the first wife might view her, even though she felt at ease after performing Istikhara prayer, knowing that she is a divorcee in her forties? And would she be sinful if she refused, and what is the legitimate Islamic ruling on this matter?

The view held by some Islamic societies that polygyny is a betrayal of the first wife is a mistaken view that contradicts the law of Allah. Allah has permitted a man to have up to four wives, as He Almighty says: (then marry such women as seem good to you, two, three, or four). No Muslim can object to Allah's ruling or imagine injustice in it.

The second wife did not 'steal' the husband; rather, he approached her by his own choice, and he will bear the burdens of both families.

The jealousy of the first wife is natural. Even the Mothers of the Believers experienced jealousy, and the Prophet (peace be upon him) overlooked it. The matter can be managed with wisdom and good character, along with enduring some of what may emanate from her.

As for accepting or rejecting the suitor, if you hope for someone better than him, you have the right to refuse. However, if you fear that someone better, or even similar, may not come along, then accepting this suitor is better. For a woman to agree to be a second wife and endure some annoyances is easier than remaining without a husband.