When I was reading the post and you got to the point where you said 'she is concerned because..." and I thought, 'doesn't want you to get hurt', then you said '...thinks I am meeting other women'. WHoa! Red flag! Mistrust and jealousy because you are riding your bike?
I am sure I am not the first to tell you this, but the age difference between you might be a signal that something else is wrong. A 29 year old is just starting their life, finding a steady career, maybe starting a family. A 56 year old is usually at the tail end of that stage of life. It is possible that you are not compatible at all, but haven't figured it out because you are long-distance. Her jealousy and mistrust may be a sign that she is emotionally immature, which could also be why she seeks a man half her age. She has a right to find love and to be happy, but not if you need to change every aspect of your self and life to fit it - it's not your job. There are a lot more people out there who might make her more comfortable in a relationship, or that she has more in common with.
The same goes for you - I am guessing that if you want a long-term relationship with someone almost twice your age that you don't want children, and that's fine, but if you do, or aren't sure, then dedicating your life to a relationship with this woman will be lost time you won't be able to get back.
Furthermore, I am sure you are a lovely thoughtful and intelligent person, but you have to wonder what a 56 year old sees in a 29 year old - yes, a firm body to keep warm at night, but being at such different stages in your lives, this type of relationship usually starts when one or both partners are dissatisfied with something, or are lacking something emotionally. IF it was an older man and younger woman, I would usually assume a man in a mid-life crisis or a man-child, and a young woman with 'daddy issues' (no strong father figure so they seek a father figure in a romantic partner). Is it possible that one of these relates to your situation?
Anyhoo, I don't know you or your lady, so it's quite likely I am wrong, and I wish you all the best!
Lots of love,
Clyde