We understand your struggle and we're here to support you in prayer and truth. First, let's address the spiritual battle you're facing. The Bible tells us that our struggle is not against flesh and blood, but against the rulers, against the authorities, against the powers of this dark world and against the spiritual forces of evil in the heavenly realms Ephesians 6:12 WEB. The suicidal thoughts and self-criticism you're experiencing are not from God, but from the enemy who seeks to steal, kill, and destroy John 10:10 WEB.
Rebuke the enemy right now and remember God's promises. You are fearfully and wonderfully made. When you were woven together in the depths of the earth, God's eyes saw your unformed body. All the days ordained for you were written in God's book before one of them came to be. Psalm 139:14-16 WEB. You are not a mistake, an accident, worthless, or stupid. You are a child of God, created with a purpose.
Let's address the issue of comparing yourself to your sister. It's important to remember that God has given each of us unique gifts and talents. Just the fact you are identifying the problem is a start to solving it. You are feeling this way because you are living in the flesh and not walking in the spirit. We are all tempted to compare ourselves to others, but this is a dangerous trap. For we dare not make ourselves of the number, or compare ourselves with some that commend themselves: but they measuring themselves by themselves, and comparing themselves among themselves, are not wise. 2 Corinthians 10:12 WEB. It also seems your perception of her is correct. It is good you are wise enough to see it. Instead of feeling overwhelmed, use this as motivation. Instead of feeling like a failure, learn from your sister's diligence and apply it to your own life. Many Christians struggle with procrastination and intrusive thoughts. It is good you are being open.
Let's pray together:
"Dear Heavenly Father, we come before you lifting up our brother/sister in Christ, asking for your divine intervention. God, rebuke the enemy and his lies. Help them to see themselves through your eyes and not the world's view. Lord, give them the strength to overcome procrastination and self-doubt. Help them to embrace their unique gifts and talents, and to walk in your purpose for their life. In Jesus' name, we pray for unity in their family and for a deeper understanding of their identity in Christ. Amen.
Be encouraged. You are not alone in this battle. God is with you, and you are deeply loved. It is good you are seeking God. Submit yourselves therefore to God. Resist the devil, and he will flee from you. James 4:7 WEB. Keep fighting the good fight of faith and remember God's promises for you are yes and amen. 2 Corinthians 1:20 WEB.