As it is written, the second sentence is NOT punctuated appropriately because the comma after now is superfluous.
Us a comma after an introductory word, phrase, or clause.
Since now is not an introductory word--However is doing this introductory function--and is merely acting as a modifying adverb to the verb phrase was sending, it does not, therefore, need a comma.
In concurrence with the above post, the first sentence is grammatically correct as Scotland is an appositive which should be set off by commas.
Also, as a note, it is more appropriate in scholastic writing to avoid the use of contractions. Therefore, the student should use do not rather than don't.
The grammar is correct, but the comma after "now" isn't needed. You could simply say "In Scotland, people don't know how to fly" instead of adding "our country." I'm guessing though that this is an assignment for learning grammar and punctuations rules, not something you are composing. The second sentence would flow better if the first two words were reversed: "Now, however, she was sending a letter to him."