Oh by the way, my son is 4, for him the way that I am preparing him is by mentioning all the things that he is so good at that the baby won't know aNY thing and he can be helping. he really wants to help. He pretends to install the carseat for the baby, he pretends it has been born and he is the dada, and all sorts of imaginative play helps him. Also when he gets jealous about the baby getting all of its new stuff is also by giving him responsibilities and letting him earn prizes and treats. so far it has worked out well for us. It's gonna be a huge transition for us and getting him involved as much as possible helps him feel important in the process.
It's normal for young children to go through a regression back towards becoming more needy and baby like at times before a new sibling is born. It's important to recognize and awknowledge it's a big change for her also and not to shame her for it. If she starts talking in a baby voice, needing even more hugs kisses etc, and overall more baby like it's her way of dealing with it developmentally speaking. it must be really hard because you are tired and being a single mom is really tough... i would try to get some support so you can take some time for yourself at least eveN just 20 mins a day to replenish your own energy stores by doing something that improves your wellness and state of mind. Even get a mani pedi, acupuncture treatment, therapy session, bath, reading, shopping, EtC.