Thanks for the question.
Your question however is not really answered by the passage. Notice that Ephesians 5:21-33 is using an exclusive relationship to illustrate a point for the whole church. This passage is not saying ‘Women, submit to Men’ or ‘Men, love Women’. It is saying ‘Wives, submit to the husband you have married’ (my paraphrase) or ‘Husbands, love the wife you have married’ (my paraphrase again).
As one exercises their choice to submit and love, they exercise that with the person they have promised to put before all others. That is best demonstrated in what Christ has done. He chose to lay his life down for his bride – his church. We all, as his bride, should submit to him.
Husbands and wives, are in an exclusive relationship together. It should be kept that way.
The question is a wisdom question. It is unwise to relate to others in a way that hinders that exclusive relationship.
One last word – God has made us relational beings, so don’t over-react here. Enjoy the friends you have and the friends you make regardless of whether they are single or married. There are not two classes of people here. We should enjoy relating together and find ways to do that. Be exclusive in marriage (so the only person of the opposite sex you should be together alone with should be your spouse), but be open and accessible in friendship (and enjoy meeting together groups). Live by grace wisely not law restrictively.