Wow, you have really got a lot on your plate, that’s for sure. When I read your post I recognized in your words a great deal of anxiety and emotion; it sounds as if you have just had it up to here and are ready to cry. Boy, do I know the feeling.
My advice to you would be, first — find a time for your husband to take your baby for an hour, and get to the nearest adoration chapel. If you don’t have one in your area, it might be trickier, but sometimes you can even just go sit in church before the tabernacle, esp. on Saturdays while Confession is going on. Get before the Lord, and allow Him to quiet your heart and mind. Sometimes when I do this it takes a full twenty or thirty minutes to unload each and every item that I am worried about, to yield it to Him, to tell Him about my frustrations, and then just sit in the silence and think about Him, and consider His blessedness. Honestly, even if you cannot pray about this, or feel that you are too distraught to hear the answer, try to get into the peace of His heart. Focus on His love, which is an ocean you can never get to the bottom of. He WILL refresh your soul. He can handle every single aspect of this complicated problem you have.
And anytime after this that you begin to feel that overwhelmed, I-can’t-handle-it, want-to-scream feeling, no matter where you are, remember the peace of your time with Him. And tell Him that you need it back, and ask Him to help you trust Him to get you through. The minute you are distressed, go in your mind back to the relief, the silence, and beg Him to commmand your heart back to peacefulness, and turn your thoughts to something good.
If no clear answer comes, though, here is what I might try: use St. Ignatius’ method of decision making. Make a list of the pros and cons of each choice before you. List absolutely everything you can think of, good and bad, for your friend staying, and for your friend going, and possibly for your friend staying under certain specific conditions, and possibly for her going but you helping her financially. Look at these reasons. Which choice, based on all the reasons, seems the most from God? And be honest. It is not necessarily the case the He requires you to go insane in order to bring your friend the dubious benefit of staying with you. After all, she may need to learn how to take care of herself, or to face her own vulnerability, or grow in patience, and grow up, period. But often the pro and con lists really can clarify for you where things really stand.
Finally, I would say this: as long as you are earnestly, truly seeking to God’s will, discerning to the best of your ability, I do not see how He could fail to be pleased with your decision, whatever it could be. And if you conclude that He seems to be asking you to continue offering your hospitality to this friend who is so needy, then He will definitely show you ways to do this without having it destroy your home life, your marriage, or your mental health.
I’ll pray for you tonight.