My niece is in jail also, this is the second time around for her.
Some things I've learned (don't know if they'll help you, but here they are):
1. I used to think loving my niece was doing things for her (paying her bills, putting money on her books in jail, etc.), now my definition is "being there for her", listening to her and when I can do so calmly, telling her the truth in short, compassionate calm sentences. If she hears me, I might say more, if she gets defensive I shut up.
2. I do visit her - about once a week. I can't fix her and I won't do things for her, but I want her to remember that there are sane, normal people (her family) who love her no matter what and always have her best interest at heart.
3. As she moves through her journey, if I want to be there for her and love her, I have to be willing to stare straight at reality and try not to flinch, control or let it get the best of me... which means an ever deepening trust in my HP (easy to say, a daily challenge to do)
4. Whatever a person thinks is right for them is right form them in terms of visiting or not. I always check out my intention when I go to visit. If I am going to show I love her and see how she's doing with no expectations and I know I can handle whatever I may see, I go. If I can't do it with that intention, or I'm in a place where I might want to change what I see, I don't go.
5. No matter how careful I am , no matter how much spiritual growth I go through, I still make mistakes. Sometimes I say something I regret, sometimes I do things I regret, sometimes I visit and wish I hadn't sometimes I don't and wish I had - and I'm trying to be easy on myself because I'm doing the best I can with what I know today.
God bless you for trying your best.