I know you know why she is shouting out but I really wouldn't leave her banshee wailing. I understand it's tough having these difficult BTs every night but her shouting for you really needs some sort of response.
If you don't want to put her on the potty that's fine, you can set the rules for BT and night time wees, but I would either go to her room or stand outside the door and verbally reassure throughout the wailing so she knows she is being responded to. Using or not using the potty is really not something to break the bond of trust over yk?
Then I'd look at routine and development. To me it sounds like 2 things. First that she is in the process of becoming night dry which for some just happens one day, for others takes months (mine took 6 months from his first dry night at 25 months until he was finally fully dry, it was 6 months of anxiety for him as he wanted it so much) and depending on her nature this could be causing her some sleep disturbance just like any other development. Second she may well need a slightly later BT. I'd probably move BT 20 - 30 mins later simply because you say you have 40 mins of messing around at BT. She might settle more quickly with the later BT and wouldn't be losing any sleep overall. As she is in the transition period of dropping her nap it would be understandable for her to need a later BT on her nap days. I usually had success in sorting out BT by responding to my DS's sleep needs, when he had serial call-backs after BT continuing for days/weeks it could generally be resolved with a later BT.
There are other ways to transition in the 1-0 of course, nap capping may be suitable or she may be ready to do more NNDs to ensure she is properly tired and ready to sleep at BT.
One way you might consider tackling the potty use after BT is to make a point of getting out of the room ie you have said goodnight and you have put the light off and left. If she tries to keep you there for another potty call you might say "You have just had a wee you are ready to sleep now. It's sleepy time. Call if you need me, night night" - leave room. Then when she calls you return (without waiting) but you treat as a NW. A NW for potty request would be no chat (or minimal and only whispers), no light (or dim night light) and totally boring. If it's only been a short time since she used the potty you can respond to her call-back or potty request by saying "you have already done a wee it is time to sleep" and "it's sleepy time, go to sleep" or whatever your usual key phrase is, repeat. You can also tell her if she needs to wee she may use her nappy.
It sounds like you need to be firm with the ground rules but also to respond in a clear and timely manner to her call-backs.
hth
