Savings doesn't need to be joint. Just in one of your names (or a combination of individual accounts). As long as you have held £62,500 in savings over the last 6 months (combined), then you meet the requirement.
Marriage is talked about all the time here!
If she comes to the UK to marry, you first have to apply for the fiancé visa. Once that is granted, she can move to the UK. After she arrives, she needs to get her name on a piece of mail at your address. Once that arrives (usually takes a bit of time to make that happen), you can give notice at one of the registry offices that accepts foreign nationals (again, usually a wait for an appointment). After you give notice, your case will be referred to the Home Office for approval. This has a minimum wait of 28 days, maximum wait of 70 days (though as you will already have the fiancé visa, this shouldn't exceed 28 days). At the end of that period, you can marry! Then once you are married, she will need to complete another visa application called FLR(M) to be allowed to remain in the UK. She has six months from the time the fiancé visa is issued to apply for FLR(M). During this time, she cannot work, volunteer, or use the NHS for no cost. So she'll need to hold good medical insurance in case she needs treatment in the UK. If she does need treatment, she needs to get a copy of the bill and proof of payment for the FLR(M) application. An unpaid NHS bill of £500 or more is an automatic visa refusal.
Whereas if you marry in the US, she can work, volunteer, and use the NHS from day 1 after arriving in the UK.
My husband and I married in the US, as it was so much easier than marrying in the UK. Even though I was living in and working in the UK at the time we met (I'm a US citizen, he's a UK citizen). We flew to NYC on a Wednesday, married on Friday, and flew back to the UK on Sunday.
Marrying in the US will have different requirements depending on the county you marry in a particular state. Usually the longest you would have to wait would be 3 days. There are NO visas to apply for (you would travel on an ESTA as normal, assuming you are eligible). Low cost and no waits. I can't imagine you would need to take more than a week off of work. Whereas if she comes to the UK on a the fiancé visa, she will be out of work for many, many months. Not to mention most people get VERY bored on the fiancé visa. Not being able to even volunteer really limits options while waiting to get married.
Marrying in the US is the most common option. But many choose to marry in the UK depending on their personal situation. There is no right or wrong way. Just less cumbersome and one less visa fee if marrying in the US. Do what is right for you two!