If in the evening you still have that much ambient light you might want to go to HSS mode on a Canon Flash ( shutter speed control ambient) Or use an ND filter to tame that ambient.
I If it was I, I would of used a Diffuser to block that hard light from blowing out her hair, or put her in the shade and control it that way.
This is just a suggestion, before you ever turn on the flash, get the background light under control. Make sure the background is exactly like you want it look. IE her hair isn't blown out, the sky inst blown out, ect... Then when you have that set up then turn on the main light (the flash) and all you have to do is match the power to your aperture setting you have chosen.
Example is you want a shot with shallow DOF you lens will be opened up pretty good and you wont need much flash. The exact opposite for deep DOF, the lens will be stopped down so you will need more power. If you run out of power bring it closer, if you cant dial down enough move it away.
With that much sun I would of also considered using a reflector to kick that nice sun back onto her face while she was in the shade or under a diffuser. I use a 7' wescott white shoot thru
as a scrim, it is perfect for what you are doing.
Happy Easter, She sure looked like she was having fun