Why not? Maybe it was never presented to her as a viable option. Maybe she didn't think she had a vocation. Maybe she simply didn't know anything about it.
Growing up in a Catholic homeschool family surrounded by Catholic homeschool families, I always knew about religious life and considered it just as real a vocation possibility as marriage. I was exposed to religious sisters from a very young age (I don't remember not knowing any). I remember having childhood conversations with my friends in which we would say, "do you want to get married or be a nun?" I myself never quite knew how to answer that. Now I do. And knowing the answer to that question has brought me more joy and peace than I ever would have thought.
So here's why I think every Catholic girl should look into religious life:
1. Why not?
Imagine this: you're an old woman, 70 or 80, looking back on your life. Maybe you're married with children and grandchildren. Maybe you're a sister. Maybe you're single. Regardless of your state in life, will you really regret having considered religious life? If you're married or single, at least you know what you could have done. If you're a sister, you'll be so glad you even thought to consider it. There is no downside to exploring the options. And, once you open your heart up to God's will like that, your vocation will become clear.
2. Religious life is an actual thing, guys.
I think we can all agree that not everyone is called to be married and raise children. Some girls, myself included, simply don't have that maternal, wife-y sort of quality. And that's as it should be. If people are worried about overpopulation, they should encourage more people to look into celibate life. (Kidding. But you get the point.) The world needs balance. Just like not everyone can--or should--be a leader (if we're all leaders, who's being led?), not everyone can or should be married. It's an amazing and selfless act to give yourself and your whole life to a single human in that way. The marriage vow, and motherhood, are unfathomably beautiful things, as I've come to realize more and more during my discernment. But some girls are called to be a different kind of beautiful. Instead of giving their life to a man, body and soul, they're called to live only for God. Body and soul. What a privilege, to be asked by your Creator to be His bride.
3. It will strengthen your relationship with God.
When I went on my first nun-run, I thought my prayer life was pretty good. Ha. In those six days, I learned so much about prayer, virtue, and giving your life to God in general. One of my favorite take-aways from that trip was a love for praying the Liturgy of the Hours. Such beautiful, ancient prayers. And to drop everything seven times a day to praise God, what could be better?
Besides learning new ways to pray, you'll find yourself closer to Jesus than ever before. As I mentioned earlier, when you open yourself to His will like that, He rewards you. The simple act of being willing to look into consecrated life makes you listen more closely for His will for you. And that gives Him an opportunity to tell you what He's been longing to tell you since He created you.
Every time I go on a retreat or convent visit, I come home with renewed peace and gratitude for God. I've never felt closer to Him than while spending time with His chosen ones, His brides. It's easy to be good in places like that. It's always hard to leave. And when I get home, I redouble my efforts to live for Him and Him alone in my present situation.
4. Meeting sisters, yes please.
So, in case you weren't aware, sisters are the actual coolest people ever. Everyone should hang out with them. That vague image in your head of a crumbling, dreary convent like the one in Sound of Music? Yeah. Destroy it. If you think sisters are boring, you clearly haven't spent time with one. They live in a freedom that allows them to be so rigorously alive--and it shows. I've done lots of crazy and fun things with sisters, including Irish dancing, playing basketball, taking the ornaments off a 20-ft Christmas tree, cooking, cleaning, playing games....they make everything fun. Trust me. You think you don't like sweeping? Try doing it with three sisters while you talk and sing and laugh. When every act is a gift to God, everything becomes saturated with meaning and joy.
5. You might fall in love.
To fall in love with God, the Author of love. What's more romantic than that? The amazing thing about being in love with God is that He loves you so much more than you can ever love Him. That's one faithful spouse we're talking about. Why wouldn't you want to give your life to Someone who gives you everything, who loves nothing better than to make you happy? Jesus weeps with joy when we say yes to Him. He is so full of love for us. It's hard to say no to a love like that. It kind of sweeps you off your feet. Like a good romance should.
All that to say, if you haven't considered religious life, do it. Talk to that random sister you see. Go on a nun run. Look up religious houses in your area. Research different orders. Visit them for a day or two. I promise, only good will come out of it.