At least 80% of what is written in this forum is based on photos, isn't it? And why are photos a credible source when commenting on how much in love the princes are or on endless issues regarding Leonor's personality - but in this case we just can't trust pictures because they could reveal that Letizia's relation to Cristina is not good
It all depends on the eye of the spectator I guess
So if Cristina shows this annoyed expression on her face towards Letizia on almost any occasion they were photographed together during let's say the last 1 1/2 years (and that was not very often) I don't call this coincidence but would suggest there is a deeper reason for it.