You don't think she knows it could cause tension? Isn't that kind of the point?
Either way, if you are not close, I wouldn't say anything unless asked.
ETA- Sorry, I misread. You ARE close. I might ask her if she has considered that this will compete with an existhing group, which could cause problems and she might think about coming up with ways to mitigate those issues. If you think she would take it well.
I would say something, but more in the guise of "Great idea. I think it would attract new families. You may want to talk to the pastor about it first and try to get in front of any issues the girl scout leaders may have. Just so you know- AHG is somewhat known as ___. If they feel this way too - you may get some pushback.".
I have never heard about AHG until just now, so I knew none of this. If you think she may not be aware of the politica stuff, I would probably ask why she thinks AHG would bring new members and what she thinks the kids would benefit from with AHG that they can't get with GS and then go from there.