Which one appears to be happening will depend a lot on which role you are in. One person’s boundaries can look a lot like ghosting to someone else. Especially when that’s convenient to their story.
Is it ghosting? Do you have any way of contacting them? Did you try? Amusingly I was once accused of ghosting a person who had me on facebook, had my email address, my phone number and even knew where I lived. I wasn’t in a good way and I stopped making active contact with her because I couldn’t manage it. She made no effort to contact me, but apparently told mutual friends that I’d ghosted her. When someone disappears and stops answering email, when their phone doesn’t work, or they don’t pick up or reply to texts then that’s ghosting.
Are they holding boundaries? If they’ve told you what they’re doing and why – like needing a few weeks off social media, then it’s about reasonable boundaries. If they’ve said no to something you are doing, that’s boundaries. People are allowed to say no, and to need things that are inconvenient to others – including time to themselves. If they’re doing things that really, obviously they should be able to do undisturbed – like going to their jobs, or sleeping – then their lack of response should be a non-issue. If anyone is demanding your attention when the timing is inappropriate, that’s a boundary violation.
Is it neglect? That depends entirely on the agreed parameters of your relationship. If you don’t have agreed parameters, then the thing to look at is how balanced and equitable the relationship is. If you have to be available on demand but they expect to be able to disappear for weeks and have that be fine – then it really isn’t fine at all. If you are asking for more than you are giving, then the other person isn’t neglecting you if they decide not to go along with that. If you are asking clearly and the other person keeps declining, you may not be suitable for each other. You may need a serious talk about expectations and needs.
When it comes to relationships of any shape, people will not usually have parallel needs and feelings. It’s important to talk about expectations, to deal fairly when there are imbalances, and to accept when something isn’t viable. Accusations of ghosting and neglect can be highly manipulative. Ghosting and neglect are damaging, and can be part of an abusive strategy.