I totally understand where you are. My daughter will tell us she needs to go potty, but most of the time, she's already gone. We keep her in the pull-up diapers for this reason (can't afford the laundry costs).
The thing with preschools and churches is that they often don't have the staff to keep up with potty needs. Some do, but most don't. I know at our church has had problems with this. More than once, my daughter has come home with wet pants because her diaper didn't get changed and it leaked.
Give it time and be patient with her. You said she's pooping in the potty? That's great. My daughter won't even do that.
There is a method you can try that a friend of mine used with good success. It has its downfalls, but could be worth it to you in the end. Basically, you wake your daughter up in the morning and take her directly to the potty. Don't wait for her to wake up. Then, take her to the potty every hour all day long. I don't remember if you are supposed to wake her up in the night or not though. This method is said to be effective in about 3 days. But, you would probably need to stay home unless you know for sure you would have access to a toilet she could use or feel comfortable traveling with her potty. Be prepared for accidents! They will happen, lol.
If you find something that works and leaves me with minimal laundry (an no pee spilled on the floor, lol), let me know. :) Otherwise, we can commiserate in this 'wonderful' challenge of toddler-hood together, lol.
God bless,
A.