After advice from couples that ride separate bikes.

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Hello! My wife got her 3 wheeled license this past November and we picked up her a F3T the same month. I was able to take her for a short ride through the neighborhood before Christmas, and she did fine. Step ahead to this past weekend. She was able to get out again for the first time and says that she will try to make a habit of riding more each week to help herself get used to it. After a few laps with me riding in the passenger seat, she did a couple with her driving solo and I followed her on my bike. Then we did a couple more with her following me.
My question is, if you are riding with your spouse on separate bikes, do you lead, or let her lead (if she has the least amount of experience)? I was told by a friend to follow in order to try to keep an eye on the unknown that comes up from behind (like tailgaters). But there is also so much to look out for when leading. What are your experiences and how do you handle it?
Thanks in advance for your information.