His daughter and baby are coming over. . . . again?

You don't, at this point she is no longer to be treated as a guest, but as family. Which means if you need to work, you simply say. I need to work. If you wish to lay down, then you say, I'm going to lie down for a bit.  I think you feel you have to entertain, or at least be there, like one does for a guest, as opposed to family, whom you are now seeing daily. The difference between the two is that for a guest, you are suppose to be there, attentive. For family you see regularly, they should understand you have to go about and do your thing.

Just a tip, when you're pretending to be two different people on opposing sides of a story you have to change up your writing style and verbiage to correspond with the two characters you're creating. You've got this imaginary husband and his alleged wife both starting their questions off with "as you know". This just makes it too obvious that this isn't a real situation. 

What you need is to divorce your husband and go find a hole in a wall and live in it by yourself.

Guess you should have thought of that before you married a man with a child from a previous marriage.  Also should have figured out that he likes having people over alot before you married him as well.

Wow. So you don't consider the baby your grandchild at all? I would love to have another baby in the family! This is family- not a guest- so you easily say "I'm going to lie down for a bit before my dentist appointment", go to the bedroom and close the door. It seems that she isn't just dropping by this time- she did tell your husband that her wifi was down and asked to come over. That seems fine to me. If she's on maternity leave, she'll be going back to work eventually. If you make this a big deal with your husband, the negative consequences are going to be a lot worse than putting up with her visits. 

Shame on you....just, shame on you.

Any polite, considerate would-be guest would inquire, when suggesting a stop-by, "Would that be a good time to visit?" 
You have every right to expect your husband's daughter to do this, and every right to ask your husband to support this expectation. It sounds as if this father/daughter have always been comfortable with "dropping in" on each other and that they have continued this practice, post-baby, without considering your feelings. The way to let your husband know is by simply telling him: You don't mind his daughter's visits but some times are more convenient for you than others. Would he please communicate that to her and ask that she cooperate? And what about him? He works from home as well? Does he just stop what he's doing when she comes by, or is this ever a problem for him as well?
That said: You seem to object to her borrowing your cable service and making noise or simply "being" in your "quiet house" as much as you mind the dropping in aspect. There is more than a hint of resentment about her mere presence. Is it possible for your husband to visit her and the grandchild at their place? What about giving her a cable service as a gift?
There are so many ways to make this a better situation without so much friction. Choose one.
Best of luck.

not much you can do about it, his daughter has a right to come over

I’m going to take the unpopular opinion here and kind of agree with you here IF she is still with the father of the baby. What’s her situation? Is she a single mother? If she is I can understand why she would want to be with her father regularly having a newborn is tough. If she IS with the father and has her own home I don’t see why she would want to be over there all the time. You need to talk to your husband about this and see if she can cut down on coming over everyday if you just want some alone time. You’re not horrible for feeling this way 

YOU are a selfish jealous CUNNT!  Why don't YOU move out?  THAT would be the best solution for everyone.  Oh and btw biittch....the earth revolves around the SUN, not YOU!