Avoid phone conversation, as it is easier to be pulled back in this way than via text. Next time she texts you, let her know that you really enjoyed the time together but you wish to move on for personal reasons and you wish her the best.

After that, you don't need to respond to her whatever she writes. If you respond, you would end up in an endless back and forth. As long as you show her the courtesy to be upfront rather than ignore her, that's enough. You don't owe her an explanation because nothing was official and you barely know her, having met her a couple of months ago and gone on three dates.