1. Is she not responding when you ask her questions? When you're texting a girl, you will typically either ask a question, or make a statement.
Example of a question text: My favorite dog breed is a Border Collie, what kind of dog breed do you like?
Example of a statement text: My favorite dog breed is Border Collies, my sister has one and they make great companions, plus they’re good at fetching.
If a girl is ignoring your texts even when you're asking a question, this means she has no interest in talking to you at all, not even enough to respond to your question. If you're making a statement, there may have been a chance she doesn't know what to say so you can always text her with another question. But if she's ignoring you, even after you ask a question, this means she's not interested enough.
2. Does it take her FOREVER to read your messages? Snapchat is a good texting platform because you will know exactly when somebody opens up your message. If it takes her a long time to open up your text, this could mean either she's super busy or she's ignoring you. If she's posting her own stories, or you post a story and you've seen that she views it, there's a good chance that she's ignoring your messages to er. This is a good sign that this particular girl doesn't see you as a high enough priority in her life because if she were actually interested in you she would try to respond earlier.
3. When she does respond, what do her texts look like? When a girl likes you, she's going to sound enthused, she's going to elaborate about whatever she's talking about, and she may even ask you questions. But when a girl isn't interested in you, she's not going to do these things. She will give you short responses and will never ask you questions in return. When you ask yes or no questions, she will either respond with yes or no without going into too much detail.
4. How does she respond when you ask her to meet up? If you ask a girl out over text and she's not interested, she will usually reject you in various ways. She could make up a bullshit excuse to why she can't meet up with you like she has too much stuff going on, she could mention her boyfriend even if she doesn't have one, or if you two are friends she will attempt to invite her friends or invite the group along. Other women who don't have the decency to respond won't even reply back and may even block you.
You may be wondering, why can't a girl just say no? Women are rarely direct, hence why they rarely say no.