Why is she avoiding eye contact all of a sudden

Start with what changed, not with the eye contact itself. If she used to send long messages with questions in them and now sends one line with no question, she has pulled back on effort. If her replies have slowed from minutes to hours, that's a different signal from a reply that is short but quick. Compare the last two or three days to the week before that. A single weird reply usually means nothing. A pattern of less warmth, fewer follow-up questions, and more gaps is the thing worth paying attention to.

Also look at what she says about herself. People who feel self-conscious often mention being tired, busy, or around people, which is them telling you the pullback is about their own state. If she mentions something you said that landed heavy, the shift is about that moment. Neither of these means she's lost interest for good. They tell you whether to keep the tone light or to make a small, specific acknowledgement.

Good replies here are usually one of two kinds. The first is a light, specific message that refers to something she said earlier and asks her a simple question about it. That gives her something to pick up without having to talk about the shift at all. The second is a short acknowledgement that the last few messages felt a bit flat, with no blame attached, and a clear invitation to pick it back up. Each one has a different job. The first keeps things moving. The second opens a door when the gap has been obvious.

You can tell a draft is the first kind if it contains a detail from her earlier messages and ends with a question she can answer in a few words. You can tell it is the second kind if it names the change plainly and leaves her an easy out. Leave out any apology for something you're not sure you did, any question about her mood, and any joke that depends on the two of you already being close.

Give her a full day before you send anything new, unless she has said she's busy or she left the conversation on a clear question. If she replied short, send your next message the following day, with something that doesn't need an immediate answer. If she doesn't reply to that, leave it for two or three days and send one light message that's easy to say yes to, like a plan or a link to something you think she'd like.

If there's still silence after that, stop. Don't send a follow-up asking if she's okay, and don't post about being ignored. A woman who has pulled back and hasn't come back after two or three careful messages has answered the question. If she does reply later with warmth, match her energy and don't bring up the silence at all.