I'm sure you'll get better answers than mine, but from my experience, it's a losing battle, and she'd likely be better at getting around your roadblocks that you'd be at building them. Might be time for other approaches.
Is she bypassing your blocks at home, or everywhere?
To add to what @maratsade said, if a true VPN was being used the joke's on her. For various technical reasons it won't work very well over a satellite connection. There's not much she can be doing and would most likely give up from frustration.
How are you setting the blocks? Is it in a 3rd party router? The HughesNet modem itself?
Another question I have is, what kind(s) of VPN(s) is she using? Are these websites? Apps? I don't know that these can be blocked from the modem, but others might know more about this.
Some VPNs work just fine with Hughesnet.
I remember the thread a while back concerning the Parental controls, but that was more blocking sites than setting times. I also remember that it wasn't working for me until I disabled IPv6 in my computer, as the IPv6 was automatically bypassing the HT2000W's control, as its controls, or at least with website blocking, only pertains to IPv4.
I'm not at all familiar with the time settings of the Parental Controls, nor how one might get around them.
I wonder if @C0RR0SIVE might have some ideas.