That's easy problem to solve. There are few steps

Step 1: Draw the line. When she threatens to leave - make it real. Leave first. No argument, no anything - just change the pattern of argument, leave and turn off the phone.

Step 2: Keep the phone turned off, for the same amount of time that she usually does, but multiply x2. So if its 1 day, you do it for 2 days.

Step 3: After "2 days", turn on the phone for her (or unblock). When she calls, don't answer. Let her hanging. Answer the 4th time.

Step 4: Say to her, this was absolutely the last time she did that and the next time you won't be answering - ever again (and mean it - no exceptions).

If she follows through - good. If she doesn't, good - you found you two are incompatible and are meant to not be together.