On Ilos, your squad is surprised to find that you can understand the Prothean warning. Later in ME3, they are surprised again to find you understand the videos recovered by Cerberus and that you can activate the beacon on Thessia. This explained off by the Cipher Shepard received from Shiala but...shouldn't Liara have received it too after she melded with Shepard? Even if you refuse at first, you eventually meld with Liara regardless in the game, which should give her the same insights Shepard had. Shouldn't she be understanding every Prothean thing Shepard comes across as well? Why can't she activate the Thessian Beacon like Shepard?