Some people are not religious at all, and very intolerant of religion. If you so much as say Merry Christmas, they will rip your head off. As a practicing Catholic, there really is no need to worry about this person’s opinion as you are definitely not a match.
Some people are not religious at all, but fit in the “live and let live” category. They may demonstrate characteristics of Christians, although their altruism comes more from a social perspective – be kind, volunteer, give to charity, help the poor, because it makes society better. This may be due to how they were raised, bad personal experiences with religion, not wanting the rules and regulations of religion, but liking the message, etc. You may find a friend here, but not likely a spouse. Once the conversation turns serious about how to raise children, and what moral responsibilities we have and why, you will be in two different places on some important issues, unless they are open to converting.
The fallen Catholics who were raised Catholic, went to Church regularly before they left home as young adults, maybe even went to Catholic schools, but no longer attend Mass or practice the faith may have different views. They may be disillusioned by the abuse scandals, or found the faith too difficult to follow as adults. They may come back, renewed by your enthusiasm for your faith and your positivity, or you may be so offended by their anti-Catholic vitriol that you have to run away. Sadly, sometimes the fallen Catholics are more anti-Catholic than those who "live and let live", but you never know where someone is on their faith journey unless you get to know them.