No, it's not necessarily easy for them to prove it. They need support, they need people who can assist them in gathering the evidence. They may need to obtain psychological evidence, which may be difficult if they haven't already been in counselling.
All that said, the types of evidence that are currently permitted under the domestic violence exemption around conditional permanent residence list a variety of kinds of proof. We don't know yet how many of those will be required in a given case for CIC to accept it.
I would be strongly opposed to any system that would require there be a domestic trial with a trial outcome, because there is no certainty that this trial outcome will necessarily correctly prove the abuse and, in many situations, many women are too terrified to ever approach the police. If we put that burden on them, I think the majority of abuse victims would not have obtained a domestic violence judgment, and we're far better off if there are a few people who shouldn't have slipped through, rather than having many people whom we haven't correctly helped.