Oh, yes, he’s got LOTS of reasons for her not to chase after DQ. We know DQ has something he wants, and that she has some kind of history with him. But he’s also accurate about her being potentially dangerous–just last episode she made moves that plausibly threatened both Emma’s and Regina’s lives, and they didn’t win without Elsa’s help. Rumple knows a lot more about DQ than we do, so it’s quite plausible that she’d hurt Belle if she had reason to.
Keeper of Belle's Gold magic, sand dollar, cloaks, purple FTL outfit, spell scroll, library key, copy of Romeo and Juliet, and cry-muffling pillow, Rumple's doll, overcoat, and strength, and The Timeline. My spreadsheet: https://drive.google.com/file/d/0B6r8CySCCWd9R0RUNm4xR3RhMEU/view?usp=sharing