Under the PHB's version of Dominated, yes, since there's pretty much no restrictions.
Some extra restrictions were added in PHB3, and the Rules Compendium fleshed out the Dominated condition quite completely. If you don't have the Rules Compendium, you should probably pick it up, since it has the final versions of the game's rules like this one.
Under the Rules Compendium's version of Dominated, the DM could force your player to attack someone or walk off a cliff, but within bounds:
- Being able to attack allies is part of the threat and usefulness of the Dominated condition! However, allies are still counted as allies, so the DM can't use something that targets only enemies, and they can only use at-wills to do it.
- Walking off a cliff requires a saving throw, and probably so should most effectively suicidal actions. It might also involve the player frowning at the DM, since there's not much fun value in dying.
If your DM's interested in using effects like Dominated, things like attacking allies are probably going to happen to increase some tension in the scene. But it's also probably worth talking with them and setting some ground rules, like: don't stab kids in the face, ever, or don't attack someone if it might kill them. If the DM does something you're totally uncomfortable with, tell them. Because some of that stuff, whilst dramatic, can have very un-fun consequences. This is kind of a lines and veils thing, where the line is you don't want your character killing their friends when they're dominated, even if can be a dramatic plot device and an amazing way to complicate scenes.
The DM can do other stuff instead, like have your character just sabotage the defence efforts.
They probably won't and shouldn't walk your character off a cliff to their death, either, because dying is boring, even if you get a saving throw.