Mixed gender friendships are fine in general, but there are some caveats to consider:
Friendships with guys are not the same as friendships with girls
True, Jesus had female friends. But His closest friends were men. He spent the bulk of His time with the 12 disciples and even more time with His three closest friends, Peter, John, and James. This seems like a good model to follow.
Proverbs 12:26 gives this warning, "A righteous man is cautious in friendship, but the way of the wicked leads them astray."
It is wise to be cautious in friendship. This seems like especially good advice when we consider guy/girl friendships. Let's face it, friendship can merge into romance without much warning. It is wise to protect your heart and the heart of others in all situations, including your friendships.
My husband and I have a long-standing rule that we don't spend time alone with members of the opposite sex. I have friends who are guys and my husband has friends who are girls, but we simply don't spend time alone with them. This is our method for being cautious in friendship (and protective of our marriage). As single girls, you may not need the same boundary, but it is wise to put some parameters on your friendships with guys.
Specifically, I think it's important to think through what you will and will not discuss with your guy friends. Proverbs 10:19 says, "When words are many, sin is not absent, but he who holds his tongue is wise." Just as there is wisdom in cautiously choosing our friends, the Bible points to the perks of knowing what not to say. There are some topics that should only be discussed with your girlfriends. Romance is an example.
I cringe every time I hear about a girl who gushes about her crushes and heartbreaks to her best guy friend. It may be tempting to get a guy's perspective on romance, but I don't think it's a good way to protect your heart (or his). There are other topics that require discretion and should be off the table for guy/girl conversations. The short list includes: fantasies about the future, past sexual behaviors, and periods. As a general rule, if you don't want to talk about it with your dad, don't talk about it with your guy friends.
I know I've said this before, but it bears repeating. Cut the flirting out of your friendships. It isn't fitting for Christians to be sexting, flirting with their guy "friends" in person or online, or maintaining friends with benefits. I know I bust out the whatever principle a lot, but it bears repeating as we consider what's appropriate for our opposite sex friendships.
Philippians 4:8 says, "Finally, brothers, whatever is true, whatever is noble, whatever is right, whatever is pure, whatever is lovely, whatever is admirable—if anything is excellent or praiseworthy—think about such things."
Make sure that the conversations and behaviors you are bringing in to your friendships with guys are true, noble, right, pure, lovely, admirable, excellent, and praiseworthy.
Be honest about why you have guy friends
Proverbs 17:17 tells us that "a friend loves at all times." True friendship is as much about loving and caring for others as it is about being loved. Real friends care for each other when the going gets tough and point each other toward a closer walk with Christ.
If your guy friends meet these criteria, great! But too often I see young women surrounding themselves with guy "friends" for all the wrong reasons. There is something exciting about being surrounded by a group of guys, isn't there? Even if they are just our "friends," we tend to feel better about ourselves if a guy (or two) likes us and wants to spend time with us. And even more often we claim to be "just friends" with a guy while we're secretly doodling his name in all our notebooks, hoping the relationship will evolve. I think it's great to have guy friends, but only for the right reasons and with the right motives.
