Away leaves a lot of room to interpret.
Only things that are consistent with "move away ... by the fastest means available" - this means move away and there is no room to interpret that as "NOT move away" or "move away less" or at "move away at a slower pace".
Whatever method you can move away that is the fastest is what you do, anything else is up to intepretation.
But the question is if you perceive a wall of fire, a cliff or lava as traversable.
Your perception is irrelevant, it is magic. As a matter of fact if you are in a hallway with an illusionary brick wall behind you, that you think is a real brick wall, and a dead end you still must go through it because that is the fastest means to move away and the magic therefore would compel you to go through it even though you do not know it is there.
If you are in what appears to be an open field but have an invisible wall of force behind you, that you don't know is there, but it is possible to go around it, then you MUST go around it because you can and the magic would make you do this. What you absolutely can't do is use 5 feet of movement and run into the wall and then say
"Oh well I don't know where to go so I am done."
The only thing the magic can't compel you to do is things that are not physically possible, like for example go through a stone wall, or move when you are grappled or paralyzed.
Maybe I'd just give a second chance to save at this point. Maybe against intelligence. I don't know.*
Why? Intelligence, perception and choice has nothing to do with it. You can be a completely unthinking plant or a construct and you would still do what the spell said to do.
*I guess this is something I would get an agreement on with my players. They would certainly agree on not suiciding due to a level 1 spell.
We also got to an agreement on suggestion.
Well houseruling is fine, but that is not RAW or in this case RAI. I hope you would get this agreement in session 0 and not when I cast command to get your boss to run off the cliff.
Also in terms of moving through walls, off of cliffs etc, I will note this is no more powerful than the Push weapon mastery which is available to lots of classes at 1st level and is at will.