I know the feeling!! Im 35 and still waiting lol...
Lord you know the desires of our hearts and I lift up my sister and ask that Jesus you would prepare her to meet a man who will partner with her in this life. One who will encourage her, inspire her, affirm her in her faith and walk with you, one who will challenge her and be her companion in this life. Lord bring her a relationship centred around you and mutual love for you. Jesus let your love flow into her life right now, that she would know that this is a time where she needs to seek you and search for you're heart first. Holy Spirit be her comforter and friend in the lonely times....surround her with awesome female friends who can also encourage her, and when she is ready, and he is ready, please Lord, bring them together.
In Jesus name - AMEN