In one of the RPGs, there were different classes of Jedi - some whose powers focused more on combat, and others whose powers focused more on diplomacy, empathy, and other more non-combat related Force skills. Until directly contradicted by screen canon, the latter is how I prefer to see Leia. It isn't that she isn't a trained Jedi, she just isn't the type we've generally seen in the lightsaber combat sequences - she's more like the Jedi librarian we saw in the Prequels at one point, as far as her Force abilities are concerned.
As an aside, this explanation also could come into play in three other matters:
1. Why two Sith - aided by Clonetroopers or not - were able to wipe out 10,000 Jedi: most of those Jedi were not really combat oriented in their skills.
2. Why Rey was able to mind trick and use Force telekinesis right away: that's where her strengths lie in the Force. Perhaps she'll never be able to Force leap, for example, for crap.
3. Perhaps Jedi whose talents *are* in combat related skills are much more in danger of being seduced to the Dark Side than other Jedi? The temptation to harness anger and pain for strength, rather than letting the Force work through you, must almost always be there for most people - since that is what you would do in combat if you were just a normal non-Force-using type person.
