>>2692185This.
Giggling, a bashful look, anything can work. The fine line is that the viewer needs to feel that the emotion is authentic.
In reality, the ways it can go are:
1. The subject is looking at, or projecting toward ME (viewer)
2. The subject is introspective, directing toward him/herself
3. The subject is directing at another subject in the image
4. The subject is directing at an unseen person out of frame
The fine line comes in the "at camera" looks. Yes, the photographer is there - but the viewer shouldn't feel "that look isn't for me" When the photographer's presence is obvious, it takes away from the viewing experience.
If you know the model isn't going to be able to pull it off - then it's kind of up to you to "set the table" - create a story for her. Make a character. Or, if all else fails, have her look off-camera.