The best way to affect the lives of your niece and mother and all you flesh/family is this passage in the Bible.
Proverbs 4:20-23 (ASV)
20 My son, attend to my words; Incline thine ear unto my sayings.
21 Let them not depart from thine eyes; Keep them in the midst of thy heart.
22 For they are life unto those that find them, And health to all their flesh.
23 Keep thy heart with all diligence; For out of it are the issues of life.
You keep your focus on the Word, Jesus, the Bible, and God and your family/flesh will be changed. Read the Bible, especially the New Testament, memorize passages, speak the Word aloud, meditate on the Word. Your circumstances around you will have to change the more you keep your focus on God and His Word. Your job is to love others. Learn how that love looks like from Jesus in the New Testament.
In the name of Jesus, I bless you with the life of God.