My aunt is the person whom does this the most. I will text her something important and I will never hear back. She only replies if it's a question. I find that rude. I rarely talk to her now unless it's a question. Sometimes I have to ask it several times. I sometimes ask if she saw the message. Mostly it is a YES answer. She has stage 4 Melanoma cancer. Is that a good enough excuse to ignore your niece? Even when I used to message my boss about something (both of them) they will read it but not respond. But when they message me for things, like to come in on my days off, they flip out if I don't respond in 10 minutes. Some of my Messenger friends do the same thing. This is why I don't have many friends. I talk to 2 people now. My friend that lives here and someone I've become close to on here. I've always thought it was polite to respond to messages and not leave people hanging. Once I replied back to someone on FB Messenger, and they didn't read the reply for 1 whole year! I unfriended that person after 1 year, because they never read my reply. Lol. I don't like it, so I don't do it to other people. I had a close friend from my old work, and when she got a smart phone, she only answered in Messenger, "K," or only read my messages. I stopped talking to her now. Are you one to respond back eventually or read a text and not reply?