Debating sending an order back on principal

Around the holidays, I placed a 40pc jewelry order. I had found a piece I wanted for me, and then bought a bunch of other inexpensive pieces for charity. The order came missing 2 items, including the 1 item that caused me to order the rest. I sent multiple messages with no responses, but since I didn't know about the 3-day ticket rule, I was SOL by the time I opened a ticket.

I wouldn't order from her again, but she was spamming advertisements about a very tempting deal. I now knew about the 3-day ticket rule, so what's the worst that can happen. I placed 15pc clothing order and one of few most relevant pieces was missing. I emailed the seller and they responded that they would look for it that evening. No response the next day, so I opened the ticket. The seller then responded that they couldn't find it. I suggested I would be happy for anything business professional in a similar price point, but no response.

I'm so torn and I feel like sending the order back would be petty as I could just eat the cost and the rest of the order would still be a pretty good value. But by sending it back, maybe the seller would change their packing process to not miss things for other customers. Although if she couldn't find the dress, my guess is she knew she didn't have it and hoped I wouldn't notice. This is a big seller with 27k items and 100+ love notes, so not the type of seller you'd expect problems from.

Should I send the order back or just take it as a lesson learned of not giving 2nd chances on PoshMark?