It would be unfair to say that Sammy is putting pressure on her. After all, he has waited for three years. Three years is quite a while and he has been pretty patient.
There could be many reasons she hasn't made love to you or I should say have sex. What I don't understand is why she hasn't come out and given you a reason for it. I mean, it's not like she has only known you for a few months. You two have been together long enough that she should feel comfortable and giving you a reason, UNLESS she was abused, then maybe she is embarrassed or even ashamed.
I was 25 when I lost my virginity to my Husband. I did make him wait for a year before I was ready. He was a saint for that. When it finally did happen it was FANTASTIC! Ok, getting off subject.
I think that you should communicate all of this to her WITHOUT sounding demanding.
Hmmm, breaking up over this? I don't know. That's something only YOU can decide. I know it's hard (no pun intended) but you need to ask yourself this... Can you love this woman and accept her without sex in your life?
Personally if it were me, I don't think I could. Sex is very important to me in a relationship. For many reasons... It's a strong connection between two people who are in love. To be able to be as close as you can be, feel skin on skin, passion, lust, looking into each others eyes. It also releases stress, and let's be honest, it feel amazing.
K. Starting to turn myself on...
You get my point though.