So, you’ve pissed off Nephthys…
Offense is inevitable, really. It’s not like the gods can come round for tea. You might have a very active god phone and even then you’re bound to misstep, since no matter how good your communication it’s just nowhere near as transparent as talking face to face with a human friend.
I view relationships with the gods as similar to mortal relationships, though, just writ large. Given that, a lot of the same strategies will work to repair the rift, or so I find in my personal experience. A sincere apology goes a long way. Don’t be surprised if She doesn’t want to talk to you for awhile. Think back to the last time a loved one disappointed you. You probably needed some time apart so you could process your feelings. She might need the same. The last time I disappointed Her she was silent for a few days running, so don’t panic right off if this happens to you.
Consider giving propitiation offerings. That is, bring Her flowers, honey, bread, beer, fragrant oils, whatever seems right and whatever She has accepted in the past. It’s almost impossible to go wrong with fresh clean water or milk. Offer these things in a spirit of genuine apology and don’t underestimate the power of the spoken word, either. You can say anything you like, of course, but something simply like “I have brought you appeasement offerings, oh Nephthys, that our relationship might be mended.”
An offering need not be food or drink, either. This is where your personal relationship with Her will come in to play, but some examples that come to mind include growing a plant in Her honor, caring for yourself in terms of diet, exercise, sleep, and hygiene (you can’t properly serve Her if your health is something you take for granted and/or neglect), community service, or anything else that She requests. Hopefully She will still be present enough to communicate Her wishes at this stage. However, if that is not so I can tell you that I’ve had good success with bread and chocolate, especially if you have the resources to bake the bread yourself.
Taking care of Her space will also help. Take apart your altar. Clean and purify all the different components, then replace, keeping thoughts of Her in your mind. A new item or decoration for the altar can also be nice. I suggest essential oils (the Mistress of the Laboratory), bath products (ritual bath associations), and lapis lazuli stones. A special ritual designed to bring your thoughts back to Her can also be a nice thing to do, and there are a lot of resources that might help you create a ritual unique to your relationship with Her. Clothing Her icon in something new and special can also do wonders. My color associations with Her are hot pink and dark blue, so my icon wears a bright pink ribbon and a dark blue evil eye charm. Your associations may very well be different, and that’s just fine.
Lastly, I find that Nephthys can be particular about how She is portrayed, so caution when you speak or write about Her is probably a good idea (don’t worry, I’m taking my own advice right now!)
I hope this was useful!