Hey there! I dare say that neither of them sounds correct in this context. In my opinion, it has the meaning that 'the room is, in terms of splendor, equal to or even better than any that Sansa had ever seen. Hope that answers your question.

"The room was as splendid as any that Sansa had ever seen. She stared in awe at the carved wooden screen and the twin sphinxes that sat beside the door." -- At first I thought it would be a transmission mistake. But I found the same words in the original. To be honest, I am a bit confused, because there seems to be incoherence between the words "as splendid as", "ever" and "she stared in awe..." -- "Ever" seems to refer to an exception, on something unusual or outstanding. If this were not the case, she would not have stared in awe at the things around her. -- So I tend to affirm your interpretation, Chino Alpha, without knowing the details.

It means that it is equal in splendour to the most splendid rooms Sansa has ever seen. So your interpretation 2 is wrong and your interpretation 1 is not quite right either, because it sounds like she is talking about all rooms that exist. But she is only talking about the rooms that she has actually seen.

Both interpretations are quite similar but I would choose number 2. She's talking about her personal experience