It is good that you are bringing this person before the Lord in prayer, especially in seasons of sadness when the heart is most vulnerable. Moments of sorrow can make any offer of quick comfort seem appealing, and that is often when the choice becomes clearest whether to walk according to the flesh or according to the Spirit.
Temptation itself is common to everyone and is not sin. Even Jesus was tempted, yet without sin. The sin comes when desire is allowed to conceive and we turn aside to follow what is suggested to us. God does not solicit anyone to evil. That solicitation comes from the enemy, and it almost always carries the promise of immediate fulfillment if we will just step off the path God has set. The testing of faith, when endured, works patience in us, and patience is so needed because our greatest failures often come from not waiting upon the Lord. What this person needs, and what you are right to pray for, is grace and strength to wait, to choose the Spirit over the flesh, and to answer every suggestion of the enemy with the truth of God's Word. The Lord does not merely give strength, He Himself is our strength and our song and becomes our salvation. He is the rock and defense for those who trust in Him, so that even when shaken they will not be greatly moved.
You are also right to pray about counterfeit influence. The enemy is able to imitate much of what God does in order to deceive. A counterfeit, however, never proves the genuine is false. In fact it proves the opposite. There could be no counterfeit unless there is a real and genuine work of God to imitate. God has a true comfort, a true companionship, and a true fulfillment that He gives to His children. When someone comes to Him with an open heart asking for His fullness, He will not allow the enemy to answer with a false substitute. Pray that this person will not settle for what only looks and sounds like love or comfort but is empty, and that they will have discernment to recognize what is not from God and to turn from any corrupting influence or any person who would draw them away from Him.
And above all, continue to pray for deliverance and salvation. The salvation Jesus spoke of and accomplished is great because it is open to whosoever will come to Him, and He will not cast out anyone who comes. It reaches the lowest sinner, it brings forgiveness and deliverance from sin, and it gives the hope of eternal glory in His kingdom. It rests not on our own ability but on His grace and His work on our behalf, and even the faith to believe is His gift. The grace of God that brings salvation has appeared, and Scripture urges us that now is the accepted time, now is the day of salvation, not to be put off. True deliverance comes from Him alone. He is the rock of our salvation and our refuge.
So let us pray together that God would guard this dear one in times of sadness, fill them with His grace to resist every solicitation to evil, deliver them completely from every counterfeit person and influence, and draw them fully to Himself through Jesus Christ. May they learn to wait upon Him, to find their strength and joy in Him, and to receive the gift of salvation and new life that He alone can give.