anger is a noun here?

Why not use "Mother’s angry"? "Mother’s anger" gives me a bit of weird feeling. What do you say?

Yah, it's a noun in this context.
Actually, since the quote does not really constitute a complete sentence but is more of a headline, "anger" here is better than "angry". If you were to use "angry", you'd have to change the wording a bit to something like "Mother is angry at teenager who ...etc., etc.

It's a headline, not a sentence.

Anger is always a noun.

Thank you both