This is almost embarrassing, but I am conflicted on how to handle this.  I have a social media account that I have enjoyed for many years.  I use it to keep in touch with my Bio family and my actual and real friends. 
My StepGrandkid23 sent me a friend request a few days ago.  I have little to no relationship with her even though I have been in the family long before she was born.  We see her once or twice a year.  She has two kids of her own.  She has a sister, (SGK19).   Her mother (OSD54) has a tolerable relationship with me, at best.  We live several hours away from all of them. 

Here's the rub:  a few weeks ago, my DH sent his daughter (SD54) a THIRD request (over the course of 2 years) that she please return something to him that her other daughter (SGK19) had borrowed a couple of years ago and had never returned. He, walking on glass as he usually does around both of his DD's, mentioned in the email that if the item was by chance damaged and if that's the reason that they were not returning it, he wouldn't be upset.  He would just really like to have the item returned to him as it was a gift from his father. 

For some reason, SD54 completely flew off the handle and tore a strip off of him (via email) that: "How dare you attack your own granddaughter that way by implying that she destroyed it!"  She also said that she is hurt that "you assume we are liars and ruin/misplace borrowed items." And for good measure, she threw in that "you avoid my calls and emails" (which he NEVER, EVER  does!!!!).  She went on to say that the borrowed item was sitting right in front of her and that because she is going through financial hardship right now and all sorts of difficult situations in her life, she hasn't had the time or money to send it to my DH.  After receiving these two angry emails from her, my DH didn't care so much about the item, as he was just hurt by the absolutely uncalled for harshness and accusatory nature of her emails.  He sent back that he ALWAYS returns her calls and emails and if he "offended her in some way, he was truly sorry, but he has repeatedly asked them both to return the item and he just wanted to get it back." and he ended the email with another apology and "love dad".  ( Personally, I think if someone borrows something, they should return it within a reasonable amount of time.  If the lender has to ask for it back, then the borrower should apologize and return it right away.  If the lender has to ask for it back on a continuous basis, the borrower should return it with, not only an apology, but with a consolation gift for being so remiss in not having returned the item promptly after the first request! )...but that's me...just the way I roll.   

Long story short, she finally delivered the item to another family member who shipped it for us.  It cost him $3.10 to ship it and he did it the same afternoon that SD54 dropped it at his front door.  Anyway, we have not heard from SD54 since that exchange of emails, and I can tell that my DH is hurting over the entire situation.  

Back to the social media dilemma.  I can't help but feel that the only reason my SGD23 has sent me a social media friend request now, after all these years, is to spy on our camp so that she can relay information to my two SD's, (OSD54 and her sister YSD47)

In the ten years we have lived six hours away from them, they have visited us 10 times.  Pretty much all ten times were the most stressful and exhausting weekends of my life, punctuated by small moments of fun during the visits.  Otherwise, I was just overworked, ignored or treated rudely and my house was completely ransacked and soiled by my two adult SDs and our SGKs who knew that the only person who was going to be cleaning up after them, after they left, was me.  After their last visits several years ago, I informed my DH that I just could not manage their visits anymore.  Mentally or physically.  I think they are now trying to see if we are still entertaining guests in our home and if so, who.  (The answer is yes, we are still entertainings guests.  Guests who are clean and appreciative of the effort that I put forth in having them here.  Guests who treat me and our home with respect and who are actual "Friends" of both of me and my DH and who don't take pleasure in trying to pit us against each other all of the time.  Guests who don't look for ways to provoke myself or my DH into having drama in our lives.)

Sorry...back to the social media question.  What should I do?  If I delete the request, (which I would like to), I will start a war in that I don't like my SGK's enough to include them on my social media.  If I accept her request, then I have to censor everything that I post, as I don't want the SDs to see everything that I post to my true friends.  Incidentally, I NEVER post Anything to do with any of my SDs or SGD on my page, which could ALSO be viewed as a slight against them.  What would YOU do?  And, any thoughts or insights on SD54's anger filled emails to my DH would be appreciated too. 

So sorry that this turned out to be so long...