Seeking Advise from Those of You Who Have Provided Kinship Care

My niece has lived with us for half a year now, along with my two year old daughter. In many ways our lives are beginning to stabilize after a fairly intense period of transition, grief and instability. My niece is an amazing child. For example, this morning I was admiring her ability with animals. We have two newer kittens. One of those kittens used to be a stray and is terrified of my two year old daughter and of my partner and I. Somehow, my sweet niece is sitting there with both kittens around her, gently touching, whispering and nuzzling them.

She also has a terribly hard time a lot of the time. She misses her Mom every day and it clearly tears into her being. She grieves not living with and not seeing/talking to her mama and still doesn't have the language to express her confusion, frustration, or sadness so it comes out as anger and fits. Many of our days feel like they are filled with screaming from the time we wake up to the time we go to sleep. Some days, everything - I mean everything - is a struggle. I discipline her using a mixture of time outs and time ins depending on the situation and circumstance. We spend time snuggling and talking about her Mom. I tell her every day, all day long, how much I love her. I try to give her as much positive reenforcement as possible. The fact of the matter is I am not her Mother and I can't properly fill the void. Meanwhile, I fear that her Dad may decide, on a whim, to take her into his care. This would not be for the best, especially because she does not know or trust him. (We are working with a lawyer but I still do not have legal rights in anyway. Hopefully I will at least have power of attorney soon.) Originally we were going to care for her for a short time, while her Mom attempted recovery. Recovery did not happen and she deteriorated further. So, we very willingly offered for my niece stay with us for longer - under the pretense of waiting until her Mom is stable again. I doubt she will recover at this point. I am worried that these two children, former only children, are going to loose each other. They are siblings now. I am financially stressed. I am concerned that my heart will shatter if she goes to her father. I am more concerned that she will shatter if she is made to leave our family (including my mom, her maternal Grandmother) after already being separated from her Mom.
Meanwhile, the fits are truly epic. Really, really intense and often. Now, I know that three is a very tedious age for many, many children. In some ways her behavior is not *that* unusual. What is harder for her (and me) is where it comes from, and where she goes once it starts. She fixates on her Mama when she is upset. She says she doesn't like me, or her cousin or my partner. She wants her Mama. Once she calms down, if it seems appropriate, we talk about why her Mama can't take care of her. I tell her that her Mom is too sick (it's the closest to the truth that feels comfortable, considering her age...and it is fairly accurate). Often, we totally rock it and do great. Sometimes, it is brutal and I feel drained, frustrated, resentful and guilty for not dealing with her fits better (I loose my patience sometimes and raise my voice - I do apologize and explain when this happens).

I am looking for any and all stories and suggestions from people who have been in similar circumstances.
How can I better give this beautiful girl the love and support, confidence and security that she needs. She needs to be built up and healed. She needs to feel like she belongs and that she is safe. Is there more that I can do? How can I keep it together and deal with my grief more effectively? I was attending a kinship care support group for a short while but because of schedule conflicts have not been able to attend. Likewise, counseling is not an option right now. So mostly, I am just looking for some comradery and kinship-care-mom to kinship-care-mom support and advice. I really want her and the rest of our family to thrive.

edit to add pertinent information:
Yes, I have been able to insure her under a state plan. Unfortunately, there are no counselors who will, or are trained to see children within our county (or the counties nearby). However, there is a possibility that we will have a bit of money coming in soon, in which case we will pay for some sessions out of pocket. I have already found a therapist who I would love to have see her.

No, we do not have a formal custody plan. CPS is not involved and we wish to involve them only if/when we absolutely have to. We should have power of attorney soon, so that we may make medical decisions, enroll her in "school" and travel.

We have a well check scheduled for early December (when her health insurance kicks in). According to my research and understanding, she has met all of her developmental milestones on time and is doing great (she is skinny and tall, but it runs in her family). Her speech is really on par with age, but she is three. So she is not able to understand what is going on, or process it as an adult would.