Well nopersonaldata the good thing about older women is that they typically know what they want and have their sh*t together (typically). That definitely sounds like the case here. If you feel that strongly about her then you need to talk to her about it. Sometimes to be the most sincere you have to just put your neck on the chopping block (i.e. come out with exactly what you feel knowing that you could be utterly rejected). If she has the same feelings that you do this will probably be a very positive occurrence. If you are also talking about having a lasting relationship with this woman you do need to SERIOUSLY consider the age difference (as Sonrisa mentioned). 21 years is a huge age gap. In just 10 years you'll be 36 and she'll be 57. At 36 do you think you'll be able to maintain a healthy relationship with someone who may not be able to keep up physically? Just three years after that she'll be 60 and coming up on social security collecting age.
You really have to be honest with yourself BEFORE you just into this. I was 18 dating a 36 year old woman. Believe me it was great and I would have married her, but a series of events happened that really made me wonder if I could handle what could happen and if I could handle the eventuality that she'd die before me. The answer, once I considered the situation without all of the emotional cloudiness, was that I couldn't. I ended our relationship and spelled out exactly why. It killed me, but I knew that it was for the better.
Maybe you can cope with the all of the things that will come along with a relationship with such an age difference, but you need to think about it now so as to save you both some heartache in case you cannot. A few more things to consider:
At 40 you will probably still be looking good and at 61 she probably won't be looking as good. Can you trust yourself to stay loyal?
In later years are you fine with playing the role of caregiver instead of husband? That may not happen, but it is a possibility given the age difference.
Your age difference will probably always be noticeable. Can you put up with the stares, judgements by and insults by others?
She will die before you do, barring illness that kills you prematurely. Do you think you can handle that heartache, especially since it will come sooner?
...one can be sure of nothing until it has already happened...