looking at some of the photos it appears there is not much contribution to subject illumination by the flash. Can you tell us what metering mode was used and when you state you were in manual mode, what does that means....manual exposure mode, manual flash control vs TTL, on camera or off? Where you using optical CLS?
As the two previous posts pointed out, "softer" light has two different meanings, one being simply the amplitude of the light and the other being the "quality" of the light. Both are important but different in application and creation.
With your scenes where the background if brighter than the subject, qualiity of light is less important than amount of light to balance background and subject illumination. Where the speed light is the primary source of light, quality of light becomes very important. In that case the relative cross section size of the light source determines the softness of the light referring to its ability to wrap around the subject and have no hard edged shadows unless the intent is a hard edged gritted less feminine look If a model is very feminine in features, you can use hard light for an interesting effect but it is not flattering of by far most models.
Working with models is harder than working with light, posing is one of the hardest skills to master. Highly experienced models make life a lot easier for a less experienced photographer. I have to assume your model was not experienced, in how she gave you difficult "looks" in at least 1/2 of the shops on the Flickr images. Minor differences in limb position and angles resulted in radical differences in impression where some were quite unflattering poses and others were much better. As I mentioned, lighting is the easy part of working with live subjects.
First things first however, what was the shooting settings on camera and flash, any modifiers on the flash, was it on-shoe? Were you spot metering or matrix...I assume matrix due to the light not becoming the dominate subject light source even in those in shade. The built in meter is useful but more us useful when you think like a light meter and realize what it is and is not telling you. Just looking at your subject in the scene, you should be visualizing whether she is brighter or darker than 18% grey which is the visual perceived mid point between totally light and totally black. Just from that quick visualization you will know to add or subtract light to what the meter reports.
To have much impact on subject illumination outdoors with a bright background, the speed light is going to need to be close. The mode of metering you used determines whether the flash is being configured for fill light or main exposure source. Spot metering ignores the general scene as a light source, and only considered the brightness of the spot you metered. In Matrix metering more the entire scene is used to calculate exposure but a bias it given to the focus point. In this mode, the flash will meter independently of the matrix metering and will calculate light output required to balance the exposure of the spot meter point to the overall scene exposure values. It is a GREAT system, two independent metering systems working to balance scene and subject, but it has limitations, as your white blown out frames probably showed. Give us some details of camera and flash settings and we can help getting optimum flash exposure. Once it all makes sense, you will use flash a lot more in all conditions including(especially in) bright sunny days.
