I'm thinking in her head she DOES have a support system in your town, you.  I'm so sorry,  I'd be willing to guess she had burned out all her relations in Las Vegas.  No advice. I'm dealing with a similarly dysfunctional SD.  Just all the empathy in the world.  Good luck. GeorgiaF

So your DH is paying "child support" to a 36-year-old? I mean, i would probably be ok with him paying to keep her away too if the alternative was her trainwreck of a life at your doorstep every day. I would clearly set some limits, like she cannot just come by without calling, he is not to give her a key to your house, and you guys will not be her on-demand babysitter, if that is even still needed.

ETA i see that SD has two adult children moving with her. If the cycle repeats, make sure DH knows you are not babysitting any step great grand kids! 

Have her over, get her a glass of something then swab her glass with a dna test afterwards.  Maybe if it shows he's not the father he will close his wallet. You have my deepest sympathy for this turn of events.  The adult skid forum is full of warriors and maybe they can help you better. Some have real pieces of work  to deal with. 

My situation is somewhat different from yours; 1) your SD is capable of working (good), ours is on disability; 2) your SD has kids with her (bad), our SD58s kids are grown.  After ske kept getting evicted from apartments, and after a disastrous 10-month stay with us, I knew we had to get her out.  I finally bit the bullet and faced the fact that 1) the wait for a Section 8 apartment would keep her in my house for ages and my health couldnt stand it.  (She was a lying, thieving druggie, I hope thats not your case.) 2)  looking at her disability income, I figured we would be subsidixing about $500 per month for a basic place in our Midwest city.  So long story short, that's what we do.  I made it clear to her and to DH that not one more penny of mine was going to her.  He and I separated finances and he pays this out of his income.  I think he also responds to some of her "emergency" requests but if he choosrs to spend his money that way, whatever.  This plan has been more successful than I expected.  He had a come to Jesus talk with her and told her this was her last chance, next stop is her living in her car.  So far, 3 years later. It's working.  Is this perfect?  No.  Are we enabling her and should we put her on the street?  Probably.  But this is working for us now.  Good luck, GeorgiaF

Wtf. He pay an adult child support??

Good Lord. 

Hope y'all have iron tight wills. 

Is your DH well funded for retirement? Will the both of you be able to maintain your standard of living? Does he have a long term care policy for assisted living or nursing home care? Does he have money saved to pay for home health care services out of pocket? If no, he's stealing from your future to subsidize a grown woman who is likely not even his. 
1. Paternity test NOW

2. NO MORE "CHILD SUPPORT" for an adult. That's supposed to stop at 18. 
3. You all are not her support system. 
4. Any money he gives her, you pull triple  out of his account and stash for your three bio kids. 

Time to tell DH that every $ he gives his adult daughter he needs to match for his other DC.   He can't treat one child different to his others because she to lazy to work.  If he doesn't then you do it.

I think it's time stop seeing his behavior as "generous" and start seeing it for what it is -selfish. He's kept his daughter dependent so he doesn't have to feel guilty. Had he cut this out years ago, she might be a self-sufficient person - or at least, she wouldn't be draining your finances. He's not being a "knight in shining armor", he's being a poor father. Time for you to start really addressing this instead of throwing your hands up and feeling powerless. 
 

As someone else said, separate finances and let him know that you will be taking the same amount he spends on her out of his account for your retirement and your 3 boys. 
 

Maybe marriage counseling could help as well. 

Essentially, he's buying her "love." And if he doesn't write that check, she punishes him. He's enabling her, and she's blackmailing him. That doesn't exactly shout love.

There has GOT to come a time when he stops paying for her and her adult kids. How about a deposit on an apartment, first month's rent, half of second month, a third of the third month, and then he's out. That gives her plenty of warning that she has to get an actual job and support herself, you know, like grownups do.

I know about SDs punishing their Dads. My SD does that when my DH doesn't do what she expects him to do. It's really sad, but DH acknowledges that he's paying the price for being a crap parent and giving her too much power. Now she expects it, DH generally complies, but every now and then mean old Merry objects because it impacts her life. The day I jump when a skid or my own kids tell me to jump is the day I'm ready for a nursing home.

I'm just a few years older than you are and I am so much looking forward to retirement. I have had a fantastic career, but I'm ready for the next thing. And the next thing will not revolve around his kids!

Best advice I read - you and DUH get to counseling ASAP - like this week since SD is already at your doorstep.  Counseling absolutely helps husbands hear the shit you've been saying for years!  You know what your SD is up to - no question bout that.  I've got similar fears about my adult SD showing up unexpected but you are streaming live with her expecting you to open doors/wallets and living happily ever after.  No way can you let her breach your threshold.  Until your DH steps up - you'll have to step up for your own damn self.  Ultimately- it's the right move for everyone.  Keep us posted - we are Secret Sisters of Step Support  caring deeply about each other.  Stay Strong!!