Will Princess Leia/Carrie Fisher have a cameo role?

voice and face.

I was out of breath when the door opened and showed us that familiar silhouette in white dressing... but when she turned back .... amagad!!!!!! yes, I think something wet fell down from my eyes.

 

The voice was taken from ANH, the face wasn`t. It`s cgi.

 

We have to acknowledge what is CGI (but I think we think the same)

As an illustration, I would say that what I saw on Leia's face was something like Google Maps : I mean, a "computer 3D map" textured with a "natural photo". It is a mix between "completely pure CGI and "absolutely analogue video". I imagine an old photo from Carrie Fisher's face was used to texture the model.

On the other end, I think that Tarkin's face was "pure CGI" : I mean, they didn't re-use a Peter Cushing photo, but textured the 3D model only with computer colours.

mmmh.... I don't know if you understand what I mean

When Tarkin face showed up, I saw immediately that was CGI, mainly because of the lips movements and because of the global skin colour (Peter Cushing's skin is more pale, CGI was more 'red').
When Leia's face showed up, I thought first "oh, they hired a lookalike actress", before reading the internet and learn that an actual picture of Carrie was used.