Oh, RDG,
I have been there and done that. I complained and I complained. I was so unhappy. One day the Holy Spirit showed me my heart and showed me my friends were tired of hearing it. And there was more than the weather to complain about. I didn't even realize I was doing it all the time until the Holy Spirit revealed it to me. I felt so bad I began contentiously stopping myself when I saw I was to begin complaining. To be very honest, once in a while I will catch myself complaining - it goes to the Cross.
We all complain every now and then. But praise God it can be put on the cross along with everything else. Glory to God. He came to set us free and we will be free indeed.
As G.R. suggested. I would definitely pray. Pray for her deliverance. To be set free from this. She may or may not be aware she is doing it all the time. Then if the Lord is laying it upon your heart share with her as the Holy Spirit leads. It may come through singing a song with her, turn your eyes upon Jesus. It may come through no words of yours but in the complete love of Jesus flowing through you. Please dont say a word if you have any ungodly feelings towards her. Just pray. But if you have nothing but the love of Jesus in your heart and prayed for the Holy Spirit to prepare her heart for His Words through you then go.
I will join you in prayer as it is love that this sister be delivered and set free. The Lord will turn her mourning into joy and give her that joyful heart of thanksgiving for all He has done for her. Giving God all the glory with you. Jesus is worthy of another soul set free. Amen and amen. May we all nail our complaining to the Cross and ask the Holy Spirit to convict us of this sin and set us free. Amen and amen!