Well she did leave and go meet up with Tammy, we know that for sure. She left even when the girls didn't come home. She was concerned enough to tell misty and heather to go find their kids, then left to go meet Tammy.
It had to have been incredibly important in order for her to go to Tammy's rather than help look for her beloved granddaughters.
In the link and quote I posted above, Tammy met Wylma at Wylma's house. No point really other than I always assumed Wylma picked up Tammy at Tammy's house to go do their "plans". I guess I should have read all this more thoroughly months ago.
To me this means the girls normally had the freedom to be riding bikes til whenever. But not that day because the girls knew Wylma had plans and was leaving soon. IMO
I know it has been debated time and time again but I feel if Wylma did not give the girls that much freedom then she would have been more worried/upset/angry. It all sounds so nonchalant. No big deal that the girls haven't come home yet and that I (Wylma) have searched everywhere for them. You take over so I can go do my thing (whatever that may have been). It feels like the girls or just one of them had done this before. So often that Wylma didn't get bent out of shape about it anymore. IMO