How do I explain how I feel about her

Read what she has actually been doing, not what you hope it means. If she replies fast, asks you questions, and suggests plans, she's probably already leaning in, and a clear message will be welcome. If her replies are short, slow, or always wrapped around logistics, she may be enjoying the company without the same momentum, and a big statement could feel like a jump she didn't agree to. Either way, the feeling you have is real and worth saying, but the wording should match the energy she's already putting in. A message that names the feeling simply, without asking her to match it, works in both cases.

Also look at how long you've known each other. Three weeks in, a line like "I'm really into you" reads as honest. Three messages in, it reads as pressure. The question isn't whether you feel it, it's whether she has enough evidence from you to take it seriously.

The message that fits this situation has three parts, and you can tell a draft is right when it has all three and nothing else. First, it names the feeling in ordinary language, something close to how you'd say it out loud. Second, it points to a specific reason, usually something she did or a conversation you had, so it doesn't read as generic. Third, it leaves the next step open. Drop anything that asks her to commit, define the relationship, or say it back.

What to leave out is the qualifier stack, the joke that undercuts the line, and the apology for having a feeling at all. If your draft has more than two sentences, cut the one that explains why you're telling her. The shape you want is a clean statement followed by a sentence that gives her room to answer whatever she actually feels.

Pick a time when you're not tired, not drinking, and not in the middle of something stressful. A weekday afternoon or early evening is usually better than late at night, when the message can read as heavier than you meant. Don't send it right after a short or awkward exchange, because she may read it as a reaction to that.

After you send it, wait. A day is a reasonable window if things have been moving at a steady pace, and longer if she's been slow. If she replies warmly, match her energy and let the conversation move naturally toward plans. If she replies with something neutral or vague, don't chase it with a follow-up asking if she felt the same. Give it a few days and let the normal rhythm return. If she goes cold or says she's not there yet, accept it and keep the door open without pushing. Most of the time, the message does its job the moment she reads it, and what you do next matters more than the wording.