It's natural for the man to be older than the woman, for many reasons which can be summed up best as "human nature".
But that is as far as we should go. I disagree with the ridiculous "10 year minimum" as suggested above. Maybe that worked out for her personally so she's going to apply it universally -- but there is no logical reason to do that.
Women can't stand to marry someone they consider inferior to them. That goes for intelligence, maturity, career, income, etc. On the other hand, normal women don't seem to be too focused on looks -- or even general fitness (weight, for example).
And yes, maturity and wisdom are important factors in determining if a given young man is ready to marry. He also has to be able to provide for a family immediately after marriage. If he's still in college that's a problem. You can't "wait a few years to start a family" like pagans on birth control.
I bring up wisdom because if you're not careful, you might end up marrying poorly:
https://www.cathinfo.com/anonymous-posts-allowed/young-men-beware-marrying-novus-ordo-women/A lot of young guys don't think enough, or they go along with the mainstream too much ("she's hot!") but aren't thinking of the future. If the young lady wasn't raised in the Catholic Faith, or with conservative values, it's not going to be part of her. She might convert and go along with a strict interpretation of the Catholic Faith while times are good, while she's "in love" (the emotion) with you, but if times get hard, disagreements arise, the honeymoon ends, crosses and challenges arise, and hard decisions must be made, that protestant, pagan, or Novus Ordo upbringing will come back roaring with a vengeance.