Invite the happy couple over for dinner and bring out the photo albums. Start reminiscing over her childhood, embarrassing stories, letting the fiancé get and education about his future wife.   Ok l, if you aren't up to that, just keep busy, too busy to participate in her stealth like mean girl games.  That's means DH will have to deal with her on his own  and maybe that's what he needs to experience.  She will force him in the middle.  Not you.  You just be your sweet self to him when he's treating you good.   Don't let him drag you into it.  If he can see some of it now, he needs a clearer vision.  Don't stand in the way of that happening.  

You and DH, not DH and SD, establish how much to contribute to the wrdding and stay firm on it.

Hahahaha! What planet does your SD live on, OP?

Why on earth would she expect Daddy to buy her a house??? 

You and your H need to present a united front, tell her to get off her lazy arse, get a FULL TIME job, and start saving, like most of the rest of the world has to.

I hope your H is not already financially supporting her? If he is, that may have given her more expectations...

pay for her Big Wedding,  

Send them on a Fabulous, Expensive, Once in a lift time Honeymoon.

Buy them the Mac mansion.  With the gold toilets.   She may get the hint   And

AND ,  AMD, It's all the falt of the evil SM.  You 

You will be disengaging and or at divorce court 

Just Ugh. We were told how we were paying for this elaborate huge wedding, it didn't happen. The next one was a few years later in a park and a pot luck. The next one was just private. The latest we weren't invited to. Good luck, she sounds like she likes to be large and in charge.

She can think what she likes.. but you and your DH need to have a discussion about what he will and won't be contributing to her wedding.. to her home.. to her life.

If you maintain separate finances.. you still owe each other the respect to discuss significant financial decisions.. you still have joint financial goals as a couple.. and need to work together to ensure you both stay on track.

So.. is he "independently wealthy"?  could he, in fact, with zero impact on your household and future.. buy his daughter a house?  has he made it clear that was a plan all along? did he help his older daughter in any similar way?  is he managing any trust on behalf of his daughter?

If the reality is that you are just normal people who are comfortable.. but not able to support two households.. he needs to break that news to his daughter.. and sooner rather than later.

"Dear.. Just as I had done for your older sister... I have X set aside to help you start your life.. you are free to spend that on your wedding.. or towards purchasing a new home.. or a honeymoon.. or paying off your student debt.. the choice is yours.. but that is the total sum of what I will be able to provide any help.  As your father, I have to impress upon you the importance of you both standing on your own two feet.  I can not really recommend that getting married while you both are still relying on your family is the right plan.  You and your Fiance both need to be independent and able to support your household.  And.. that means you need to probably be working more than a part time job.  I can't force you to do that, of course.. but I do not have to continue to support you financially.  If you are mature enough to be a married woman.. you are mature enough to figure out how to support yourself.  I love you and want the best for you, but there is a limit to what you can expect from me since you are telling me you are an adult and capable of making your own life choices. So.. again.. I have $15K set aside for you.. to use as you wish.. but you need to understand that is the last I am able or willing to provide.. and you will need to learn how to live within your own ability and means."

with this one.

So- without diving too deeply into your financial sitch - is it realistic that she would expect that daddy-cakes would buy her a house?

How do you manage them? Do you have a prenup?  What is your DH's position on helping her buy a house and paying for her wedding, etc.?  This might be the kind of issue I'd get a divorce over as it would be a big financial red flag for me, especially if it affects your retirement plans, etc.