Word of warning.
I was in this exact position, and that one switch to J has now cost me a lot of money as my wife no longer wants to sit in economy and I am now purchasing the additional tickets in J.
Missed seeing this the other day. SWMBO not only refuses to sit in Y but also expects to be in her preferred 1A seat. Given my (fortunately temporary) drop from Gold, when I could not book 1A…. I can tell you that I have suffered some icy glares when she has to sit in row 2.