It's definitely a result of post processing, but the fact that the first image features model partly submerged in a milky substance helps of course.
As already pointed out in the comments a common feature of the four photos is the fact that they lack absolute black. This is easy to achieve by raising the left part of tone curve. They are also desaturated and the contrast is lowered. as this kind of editing will adjust both brightness and colours a lot a huge advantage will be gained by shooting in raw. This will increase the number of available tones and will certainly improve the final result.
The second photo is clearly over-exposed which in conjunction to raised blacks gives the image a "soft" feel. Even if it hasn't to do with the milky tones the depth of field is also quite shallow and further adds to the already soft feel. Look at the hair: it's sharp near her face but it gets blurry further down. It's shot at ƒ/1.4 with a 30 mm lens and at a distance of 1 meter it corresponds to a depth of field of about 6 cm with a Canon Rebel T2i. Using wider apertures also tend to make the images softer (i.e. less sharp) and 3 out of the 4 images are shot wide open.
Of course we may never know for sure what has been done to the images unless we ask the photographer. Have you tried sending a message to the photographer? People are usually very flattered if someone asks them about the technique they are using and I'm sure she will share it with you if you're polite and pays her a compliment. Someone asking about the photos means they are doing things right and actually engages with other people through their photos. After all Flickr is a community and one of the main reasons to post content there is to get some response.