Is the ph and temperature of the water you are changing with the same as the tank when it's leveled out? Could be a factor, an example is my well water depending on the time of year has co2 in it making it more acidic and when water is left in bucket is alkaline, fish don't enjoy going through an instant ph swing weekly or daily. What is your tank temperature? Keep around 27C* normally if she is clamping I'd try slowly raising the temp to 28 or even 29 an angels immune system is stronger at higher temps, only let some window light in for a few days and no tank light the subdued light will keep her calm, sometime try to block out half ur tank light and see if she hangs out on the darker side it's a good indicator she's stressed. What's your ph of your tank? They enjoy more acidic but don't try to get it down if alkaline unless it's over 7.6-7.8 and only use natural ways, don't worry bout that now though just a tid bid of info, it would stress her more to change it and cause problems. I'll edit if I think of some more things to try.
Best of luck
