Making different kinds of money can be a real issue! I have felt it because I make many times more money then my BF. He would not even be able to visit me (witouot saving up for several monts). I pay all of our expences and he resents that a bit, because he is independant (or tryes to be) and because he does not think a woman should pay. But the fact remains that until he gets another job (in which case he needs to finish his part-time studies) this is the only way for us to stay together. My deal with my husband is that I will cover all, or at least most, of the expenses related to my BF. This way, my husband can spend his Money on himself and has no reason to resent my BF for econonical reasons. Actually, me and my husband has started living very economically as of late, which also benifits my husband because he gets more Money for fun stuff. Ask her not to talk about Money if it annoys you, or be patient that she has Money worries that trouble her, but then allow for You to bring YOUR Money worries (or other worries) to the table, too.
If you should choose to use a baby sitter when he is away, she could split in to cover the charges. Then you could date yourself, or just have a fun night out with Girls or go see a Movie. If you don't want to leave your kids to a sitter once a week, still you can go out on a different day. That is only fair.
Her complaining about not having a husband and child can be envy. She might not want to move in with you because, to her mind, she can never have what you have. Are you ready for her to have a child with him? Are you willing to fight any legal issues in order to secure her safety and the safety of her future child? Are you ready to split Your Nights in half? Do you want Your children to also come to her when they want something (even the cute things)? Are there potentional Money benefits that could come from living in the same house? Would she consider spending less Money on trinkets in order to join Your household? Do you think she loves your husband - and are interested in getting to know you well enough to share even more of him with you? Are you ok with him in the future reffering to her also as his wife?