If Lady Onion'd had had the possibility to call another number, she would have never called Song Shuhang—not even if she was beaten to death!
After all, calling Song Shuhang implied giving up the 'freedom' she had obtained with much difficulty on her own initiative.
Someone that could already enjoy freedom had no idea of how valuable it was.
On the other hand, Lady Onion had been locked up for 300 years by Nine Lanterns right after she'd completed her training and descended from the mountain... After that, she ended up in Song Shuhang's size-reducing purse because she sought death, and stayed in there until recently.
As such, in Lady Onion's eyes, not even a mountain of gold was as valuable as her freedom.
She had finally managed to get rid of Song Shuhang and obtain her precious freedom... but now, before she could even properly enjoy it, she was forced to hand it over on her own initiative.
Did you now understand how she felt?