As a daughter who doesn't even think to pick up the phone until after midnight when life winds down, or when I'm sitting in a movie theater, etc, I love it when my mom calls me. She used to call and complain when she hadn't heard from me in as little as two days, and while I understood that she loved me, it would make it difficult when I WOULD remember to call, because I didn't want to call and get the guilt trip. Nowadays I can just chat with her, and we both enjoy it.
In your situation, though, two weeks is a long time, especially when you've been sending e-mails with no response. Have you talked to her at all since you've been home, and did she sound somewhat angry? Maybe something happened when you were there that upset her or her husband that was misinterpreted or that you don't even realize bothered them, and they are upset (adult kids can be very sensitive).
Also, I agree with the thought that she might have some post partum depression, especially since her husband is gone a lot.
Then again, it could be something as simple as you had her e-mail address wrong, and she's been upset because you haven't contacted her!
Definately visit her, or at least call, and I agree about letting her know that you miss her and you have this motherly "need" to speak with her more, but if she still doesn't call regularly, just check in a couple of times a week, and talk to her very cheerily, and without making her feel guilty for not calling. Unless her brain is mush like mine (*grin*), she'll be more apt to call you next time!
Speaking of mush, I just woke up, so hope my rambling made sense!