What does it mean when your ex says no whenever you ask her if she is seeing someone and also tells you not to ask her that again?

Because its NONE of your business. She's no longer with you, move on and stop bothering her.

At Scott says... what it means is she is telling you its none of your business... which it isn't.

It means that she is your ex and she wants you to stop asking her.

It also means that you are spending way too much time thinking about her love-life instead of moving forward with your own.

Live your own life and leave her to live her life without interference from you.

LOL...your EX? Why are you asking your ex if she's seeing someone? Why does it matter? She is your EX.

It means you are being too nosy and to stop.