tough love time. she is an adult and needs to get over it. DH needs to correct it dont think there is anything you can do. sorry

probably just a phase... hopefully, she'll get bored and move along...
Does your DH not think that all of her texting, pictures and videos are a little on the wackadoodle side?

If she were nine or ten I would probably say it's normal, definitely weird and annoying, but normal for her to have some jealousy and fear of being "replaced"

18? That is so weird to me. I have a sibling twenty years younger than me and I cannot imagine acting like this when she was born and I was twenty. Not to sound like a totally horribly person, but I didn't care at all as I was living my own life in college.

Be glad she lives in another state and is not showing up on your doorstep.

Ignore her. Let her keep making a fool of herself, and concentrate on your family.

How does your husband respond when she does this?

If she gets no reaction, hopefully, she'll tire of it soon.

Is she still in high school? It maybe more like SUCKING UP for new car, college and money money! That is just my thoughts...My oldest SS is going on 36 years old...daddy is nothing but a money tree.

Oh puke! She is an adult now ffs.

I feel bad for you OP.

Though it's over the top silly that she feels she'll lose her father to an infant (unless Dad doesn't pay much attention to her to begin with), if it doesn't bother your DH or take his time away from his own home and baby/you, why does it bother you? Why would silly stupid texts and photos along with 'Im still Daddy's little girl' destroy your marriage?

She lives not near you, she's not in your home and DH can put a limit on the contact at anytime he choses. He does have to stop and read every text the minute it arrives. Can allow phones calls to go to voice mail. Doesn't have to share videos/photos/texts with you. Hell he can just delete and/or ignore anything or whatever parts of it he wants at anytime he wants. Sure she's legal adult age now. Sure, she's feeling insecure and worried she'll be forgotten (very likely for no good reason). But in my opinion you're totally overacting to it. Are you afraid her silly nonsense is taking away the glow surrounding the new baby aka as in your husband's sole focus and thought of parenthood should be 100% on the new child and to hell with his older daughter.? (Not saying you are, I'm asking because I sincerely don't 'get' why some annoying twit having security issues from far away is going to destroy your marriage...all the guy has to do is say 'enough daughter of mine, cut it back some' whenever he chooses).

Tell DH you don't want to hear anymore about their numerous contact and that you'd appreciate it if he'd hold off when and how he responses to her endless attention seeking. It's rude to take her silliness during dinner, while he's feeding baby, while you're having close family time blah blah blah. It's totally ok to say 'DH put that stupid phone away, you can respond to her later', 'DH stop showing me the pics and videos, I don't need nor want to see them in my face 24/7' Surely the man doesn't expect you to be as desiring to know every last detail SD is saying/doing 24/7. It's not your daughter, it's his. Thanks but no thanks. You want to focus on your baby, your home and your adult time. Don't make it about the stupid Daddy's little girl thing, make it about the rudeness of being interrupted everytime his phone goes 'beep'. It's rude, it's intruding and he needs to keep it from affecting the rest of the household.

I know everyone here thinks 18 is super old and should have rid themselves of those pesky parents years ago. But, she's still pretty young. And to her, her Dad is starting a new family. I think some of you need to step waaaaay back and for one minute think about how the girl feels? I'm almost sickened reading some of these responses. LEAVE this relationship alone. It has NOTHING to do with you. She cannot take anything away from you that he doesn't allow. She is no threat to you.

Trust your husband that he can do right by you, be grateful you have him for your daughter and leave their relationship well enough alone.