I don't know if YOU can remotely access HER wireless router.  I have used the free version of LogMeIn successfully to remotely access my home PC and use it, the applications, resources, and peripherals as if I was right there in front of it.  Really cool stuff that really worked.  I could use my home PCs applications, printers, and other services with no problem.  I never needed to modify my router's configuration using LogMeIn so I can't tell you if it will work or not.  Maybe an email to LogMeIn support may get you a better answer.

In as much as you both have the same router, the process should be the same and you should be able to walk her through the process over the phone on how to secure her network with WPA2 just like you did for your wireless network.

Then again, Hughes Network, like everyone else, is looking to increase their receivables.  Putting more money in the bank helps keep them in business.  Unless she is doing her own network monitoring, it would be difficult to believe and accept Hughes reasons for her to improve her ISP plan.  Certainly not to accommodate a snoop/hacker who is stealing her bandwidth. 

If Hughes was truly customer oriented, they would have assisted her with securing her network with WPA2 and give her a tool she can use to monitor her bandwidth usage over time.  Her network usage data could help her figure out when might be a good time to unplug the router so the thief can no longer steal from her should the thief be smart enough to crack the encryption.

Good Luck,  Jim Baldwin

Generally most home routers and even big industrial firewalls can be set up to be maintained from the WAN (external) interface via https.  However this is generally disabled and your sister-in-law would need to enable this from her end. I am guessing this is not possible?  I have set up my home firewall (ZyWall USG50) to be accessible from work since I know what IP blocks Chrysler owns.  Access is allowed only from those blocks.