Welsh independence, as a movement, has an unusual amount of momentum at the moment, which most speculate is tied to the Brexit vote (probably predominantly the 48% who voted remain), and the Welsh Government's COVID response being strongly viewed as superior to Westminster's. This put devolution's practical effects squarely in the public eye in an unusual way.
The original poster is asking for personal stories about why people have changed their minds on independence - a timely question given the exponential growth of pro-independence movements like YesCymru. Her own personal experience relates to Brexit, but she is not furthering a claim that Wales' right to independent nationhood rests on mistreatment during Brexit.
Scotland's claim to independence doesn't rest on Brexit either. Zeb1 notes the Brexit referendum as something that enhances their "right" to be independent. It does not. The way EU membership was deployed as a threat during the original Scottish independence referendum, only to be snatched away from them anyway, increases their right to hold another referendum. It is a major, material change of circumstance that could be validly used to justify asking the question again now, rather than in a generation as was previously suggested. But it has absolutely nothing to do with their identity as a nation: a nation that should be allowed to voluntarily decide whether they remain in the UK. That is a separate matter.
The same is true of Wales. If we accept it as a nation, then it has the right to self-determine whether it wishes to voluntarily remain a part of the Union. This right is not based on its finances or its political alignment, those are simply things that will affect the choice its' people make.
If you question whether Wales is a nation, but London isn't, or Yorkshire isn't, well...what's the test? How do you determine nationhood? It's not easily done, but the Welsh have viewed themselves as distinct from the English, and maintained distinct cultural and linguistic traditions, for 800 years - despite an active campaign to integrate them. I'm not trying to draw some direct comparison here between the colonisation of Wales and horrors of what happened to many nations under Empire (nor to disavow Wales' and the Welsh's role that era). But they did try to beat the language out of us. They did try to turn us into an English county, and consistently, for centuries, that identity was not adopted.
So I don't think there's a clear line you can draw that says "this here, is a nation," but "this over here is a region". But I do think that as far as Wales is concerned, it's clearly a nation, and this is - for practical purposes - settled, or we wouldn't have a parliament.
If you are instead curious as to why someone might believe Wales would vote Brexit followed by independence when the former is historically aligned with right-wing concerns and the latter more aligned with the political left? Then that's a more interesting question.
It's not one I have an answer to, but I do believe that the Scottish referendum, Brexit and COVID has forced a lot of Welsh people to pay more attention to their position within the Union. While they may seem like polar opposites, it's worth noting that both are based on a belief that a distant governing body that knows little about your local issues shouldn't be in charge of you. A lot of the surrounding political calculation and culture are very different, but there is a common core.
A Welsh Brexiteer who wanted to wrest control back from the EU, only to see Wales' autonomy undermined by the Internal Market bill and similar, might feel like a little more leaving is just what's in order.
Or, the way Wales is treated in the aftermath of Brexit might be a sharp wake-up call that Leave was the wrong choice.
Or, over time, people's opinions may simply change. In 1979, 20% of the Welsh favoured devolution. In 1997, it was 50%. A referendum in 2011 on increasing devolutionary powers was 64% in favour. In 2021, perhaps the pendulum towards autonomy will have swung even further.
My personal story is similar to the original poster's. Until a few years ago, the idea of independence might be a romantic daydream but practically speaking, no, I thought we were better off in the Union and better off in the EU. I believed that the economic costs would be too high. We wouldn't collapse, of course, there are far poorer independent countries out there, but our standard of living would fall too far for me to find acceptable.
Now? I don't know that I'm fully committed to the idea still. It's hard to find unbiased economic information. But I'm definitely no longer as opposed as I was. The benefits of this broader association are disappearing. The EU has gone. The benefits of being in the UK lessen as the economic damage of Brexit becomes clear. If Scotland goes, it will be further damaged, and the political landscape will even less represent what the Welsh electorate value.
It's accurate to say that 40 MPs is a fair number based on population. But when those 40 MPs rarely reflect anything like the make-up of the English MPs, the decisions that get made rarely reflect the concerns of Wales. This reflects the anger that many understand in Scotland - that they so violently opposed leaving the EU, but must anyway. Wales elects MPs on a manifesto that will never likely be enacted. To an extent yes, when your area is opposed to the majority of the country, you suck it up. But when it's so consistent and so continual, people will begin to ask how long they have to suck it up for, and what they are getting out of the arrangement.
We are told we get economic support. But really, it's hard to know how much. It's been 40 years since coal died, and the Union has done a terrible job of lifting us out of poverty. Welsh Conservatives would place the blame for that at the feet of the Welsh Senedd but it's hard to see how when economic policy has been devolved piecemeal and is still very limited. They didn't even have tax varying powers til last year. Capital projects that might have rejuvenated areas in serious need, like the Swansea tidal lagoon, get nixed at Westminster, despite Senedd support. Valuable natural resources like water get pumped over to England essentially at cost, run by English businesses, so it's never reflected in our GDP.
It's a difficult issue, but I definitely feel there's been a sea change.