Honestly, they could meet anywhere. If Hale is desperate enough, she could just run into the MC at a grocery store and go “WHAT, YOU HAVE RED EYES TOO, YOU UNDERSTAND GUARDIAN DEVILS, SO YOU NEED TO HELP ME”
Why Hale is mad at Spike could vary. She could resent herself and her own nature for giving her a guardian devil instead of an angel.
Spike may have a personality that just isn’t compatible with Hale’s, and she finds him too difficult to deal with.
Either Hale or Spike could have not upheld their end of a mutual deal.
Either Hale or Spike could have done something without consulting the other, and both could consider it a betrayal of trust in one another.
Either Hale or Spike could have lost faith that their partnership was beneficial.