I need some information please.

My wife and I have been together for twenty five years. She was eighteen when I met her, twenty seven for me at that time. I had been divorced from my ex who had some of the same problems, just not as bad.
My wife likes to give me oral sex, it started when we were dating. No matter how much sex we had, on the way home I got antoher oral satisfaction.
She raked me with teeth every time, that made me sore. I have told her many times that I enjoy vaginal sex far mroe than oral sex. Its been that way all my life.
Yet she gets upset over this. Over the years she had come up with the idea that a blow job should be better than vaginal sex for the man. Thats what her friends say anyway.
She had some medical problems that kept us from having sex for months. she gave me oral sex and masturbated me regularly. It is upsetting her that the nead is a bit big for her mouth.
She talked with her very good friend about this. She told her that has never been a problem for her. She then ask her friend to try that on me and see if it fits her mouth. Her friend said she was not giving me a blow job; friend or not. It floored me that she ask her.
I am satisfied with what she does for me, and we have all the vaginal sex we like now.
How can I assure her that this is not a problem? Tell her or assure her that its fine and not an issue? She does not seem to take my word for this.