What advice did Marilla give Anne regarding etiquette? What news did Mrs. Lynde consider dangerous?

From the text:

The trouble with you, Anne, is that you're thinking too much about yourself. You should just think of Mrs. Allan and what would be nicest and most agreeable to her," said Marilla, hitting for once in her life on a very sound and pithy piece of advice. Anne instantly realized this.

"You are right, Marilla. I'll try not to think about myself at all."

Mrs. Lynde considered the news that they'd hired a female teacher to be dangerous.

The trustees have hired a new teacher and it's a lady. Her name is Miss Muriel Stacy. Isn't that a romantic name? Mrs. Lynde says they've never had a female teacher in Avonlea before and she thinks it is a dangerous innovation. But I think it will be splendid to have a lady teacher, and I really don't see how I'm going to live through the two weeks before school begins. I'm so impatient to see her."