For ease of writing, I'll just write this post as if the characters were real. Too time-consuming to insert the necessary qualifiers, authors' intentions, how characters are presented, etc.!
From Shepard's perspective it's like the next day, everyone else 2 years later. Plus, for Liara in particular, it's known he was DEAD because she rescued his body (which I don't think the Shepard character knows, it's in the comics which I haven't fully read). Given her actions, speaking louder than words, she may expect Shepard to know from Cerberus her role, surprised and hurt he didn't contact her after "awakening" even by a message (she's only on the 2nd set of recruitment missions...), etc. Similarly with Ashley, could have sent a message via the Alliance.
Also (pardon the mild sexism for humorous effect), as anyone with a female SO knows, even if it was IMPOSSIBLE to communicate ("I was dead/stuck on a subway between stations with no cell phone reception/whatever) it's still somehow your fault for having failed to do so...
So presenting characters as having mixed feelings - e.g. Liara, have her actions saving Shepard hurt others, she feels a duty to them, unconsciously "blames" Shepard because rescuing him hurt them, she (or Ashley - ME1 conversation she has strong belief in God) has conflicted religious feelings with Shepard being alive again, whatever the creative people had in mind - makes sense.
Others, even though commenting he was dead (e.g. Tali when first met), may think it was like heart stopped dead, frozen in carbonite dead, whatever. Incidentally, being frozen and exposed to vacuum (and then later body in stasis? I haven't read the whole comic series in which Liara rescues "your" body for Cerberus) actually kind of makes sense, that freezing and vacuum might plausibly preserve cell information, brain matter and neuron connections etc. such that "you" could with nanotechnology be restored with memories. The matter-of-fact way in which characters react to Shepard having RETURNED FROM THE DEAD suggests that in the fictional ME universe, this achievement is a technological breakthrough, but that similar things may have been done before (for shorter-term death/vacuum exposures/whatever).