The best option for "visiting the US first" is the tourism route which you already tried.
What will you do if she doesn't like the US and want to live here? End the relationship? Move back to her country?
Are you sure you are ready to marry?
If you are committed to the relationship, the best option seems to marry now and pursue spousal visa.
Yes, it's a bit ridiculous to ask someone to commit to living somewhere they aren't even allowed to see first, but that's US Immigration for you!
At least we have free video calling today, and it's a bit easier to portray what life would be like before she arrives blind (hint: It's NOTHING like what Hollywood portrays!)
If you aren't committed to moving anywhere in the world to be with your spouse, you could roll the dice and try a fiance visa, but it's an expensive time consuming gamble with a couple years of your life. Definitely don't rush into a marriage before you are ready, but also I'd be hesitant to put things on hold for 2+ years while I decide if this is the right partner for me. In my case, I was sure, and we used our 17 month waiting period to plan a religious ceremony in her home country (after doing a civil marriage through the state of Utah, in order to get the ball rolling on the US immigration side). This made the time go by rather quickly, and was fun for her.
If you are still unsure, I would probably visit more, make video calls with both families, attend some religious or couple counseling, maybe bring a sibling or best friend over to meet her, or whatever you need to do to decide you are ready for marriage. Remember, If you went the fiance visa route, you only have 3 months to decide this.
My total cost for IR-1 spousal visa (2023-2025) was $1,215 to the US gov't and $1,704 total including foreign medical fee, which varies by country. Last I checked, K-1 cost is at least $3,000 in US fees. And then you only have a 2 year green card which must be renewed ($$), vs a 10 year one that can transition to citizenship.
I was also able to receive thousands in tax refunds by revising 2 years of US income taxes at the lower "married filing jointly" rate after marrying, during the visa processing period. This was a huge financial savings, which more than covered the costs of our immigration fees, wedding, and honeymoon.
Anecdotally, my wife is fine with the US (doesn't love or hate it). One of her biggest complaints (that I hear other foreigners echo) is poor transportation and how considerably less social things are here, and everyone is just focused on working (often multiple jobs). We are likely moving back to her country one day, probably after my parents are gone, but she generally enjoys her new life here. I did promise to send her home once a year.
One of my best friends married a foreigner, who has been in the USA about a year, and she is NOT happy at all... they are a committed couple with a young daughter but I'm not sure what is going to happen. It's definitely something to work through ahead of time as much as possible. Maybe she can start talking to some expat groups on facebook from her country. My wife found several friends that way.
Edit: After reading @TexasRafael s post above mine, Utah marriage is a viable option for a same-sex couple who wish to immigrate to the US through Immediate Relative (spousal) qualifications. Utah allows couples to marry from anywhere in the world, whether you are physically together or not (but you must have one meeting to "consummate" the marriage before filing US I-130). Basically once married by Utah, you are legally married in the eyes of the US government and free to sponsor your spouse as an immigrant.