IF you have observed that mature Christian women prefer the company of other mature Christian women, I'd agree with you. There's a certain comfort level that kicks in after awhile. Women understand other women. They've shared similar experiences (especially if they are frustrated with the dating world, for example). They can talk and be themselves and feel understood and talk about faith with others who want to talk about faith.
I'm not saying that this is entirely healthy. But it happens when women are busy with working (aka supporting themselves) and involved in ministry, and so in their precious spare time, they just want to relax, have fun and feel UNDERSTOOD. Who better to feel understood by than another woman? They may not feel like they have the energy to hit the dating scene, get their hopes up, get rejected or have to reject someone. It's a lot of work!