if you make a copy and mail it to her, whether it's a loan or for her to keep permanently, you would be breaking the law. that much is crystal clear.
you have written consent from the publisher to lend her the original magazine. i believe they extended that consent in appreciation of the trouble you took to ask them.
no matter what anybody else tells you, it would be illegal and unethical to send her a copy.
this is not about what we can get away with. it's about what is right and what is wrong.
sometimes, it's less convenient to do what's right. that doesn't change our obligation.