You can say, "I hadn't met her since we broke up until I ran into her in the market."
There are three events in the past: meeting her, breaking up, running into her at the market.
You can't use "I hadn't met her since we broke up" without some other event in the past that happened after breaking up. That event is supplied in my extended sentence (running into her).
2. is a sentence out of control.
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