If it's poor etiquette, it's already been done. But I just sent an email to my aunt requesting my cousin's email address so (and I mentioned this in my email to my aunt) I can ask my cousin if she received my gift. I shipped her a gift in June. She probably waited to open it until her shower on July 5th. Her wedding was August 2nd. I still haven't gotten a Thank You card.
It's happened before where I never asked the gift was received and now I wonder if my friend got the towels I bought her last summer because it's so unlike her to NOT send a TY note. So, I don't want to wait too long for this one, but wonder how long I should give my cousin before I ask directly.