Sources state that she was queen of Solitude, which is where the High King or High Queen lives. Since Potema was ruler of Solitude does that mean her husband was High King? Did she then become High Queen?

Most likely.

Solitude is where the last High King lived. If Ulfric wins the civil war, you can imagine he would keep the Palace of Kings as his seat of power. The High King/Queen is just the Jarl elected to rule at the moot, is he or she not? Potema was Queen of Solitude, which can also be read as Jarl of Solitude. As we recieved no evidence or her dominion extending over the entire of Skyrim, we can assume the other holds can act as the capital just as well.

I do think that Potema was High Queen, but I'm pretty sure Solitude is not always the capital of Skyrim.

I believe that Potema was the High Queen of Skyrim in reality if not officially. You get the impression that she was a very powerful ruler, with many allies and it took the Empire years and years to finally defeat her. Even with her Necromancy which didn't seem the manifest itself very strongly until later in the war, I just don't see how the Queen of a single hold could pose such a challenge, her personal domains would need to be much larger, hence I would consider her to be the ruler of at least a large chunk of Skyrim, if not all of it.

Personal holdings are not everything, and besides, from what we have learnt of Skyrim's economy, Winterhold and Whiterun are probably the only other holds that could match Haarfingar. If we can assume she also had the Jarl of Whiterun in her pocket, you can see how powerful Potema could have been. Also notice that a lot of the allies she makes are not in Skyrim; Solitude is a port, so really it has access to most of Tamriel. The earlier model for Tamriel, not seen so much since Oblivion, is this very devolved, feudal system of lots of Kings and Queens, dukedoms and so on, all under one Emperor. You'd be surprised how (in real history too) powerful a lone Queen can be.

Potema is a bit different than any regular Jarl of Solitude.. she had ties to the Septims. Besides that, she was ambitious enough to try to become Empress. Even without a title, she'd be royalty of some sort, at least.

PO TE MA

MAN NIMAR CO

ADO RING FAN

DRAGonborn! Wolf-Mother of Dragons.

King/queen is a common gloss outside Skyrim for "jarl"

There was another thread about this a few weeks ago.

The answer is probably. A member of the royal family, married into the royal family of Solitude, k? Solitude being where the Empire chooses who the jarls will have picked their High King or High Queen from. So when her husband died, she became Queen of Solitude and therefore High Queen of Skyrim.

This is all my own assessment, though.

Imho, if Potema was High Queen, there is a reason we never heard of it. The reason I'd guess is the devolved, heavily feudal operation of the Empire - the title of High Queen actually being of less note than Queen of Solitude. That is, the powers available to the ruler of Solitude outweigh by far the benefits one would receive from being elected High King or Queen. Jarls themselves being essentially kings, it is likely the title of High King would be of little importance -with no tithes connected to it, no real power considering the authority of the Emperor. The only time the High King would be important, would be in the time of instability or civil war. Essentially, Ulfric only cared so much for who the High King of Skyrim was, because he envisioned an independent Skyrim.

With that in mind, Potema probably claimed the title of High Queen during her revolt, in an attempt to rally the other Jarls to her cause. It is likely the title of High Queen would have little else use - no one outside of Skyrim would pay it much attention. It would be her control of the considerable resources of Solitude, and her position in the Septim dynasty that really mattered.