Rachel Elnaugh was the only woman in the original Dragon's Den investor panel.
The original British lineup consisted of Duncan Bannatyne, Peter Jones, Theo Paphitis, Rachel Elnaugh and Simon Woodroffe. Elnaugh therefore occupied the sole female position in that five-person panel when the BBC programme began.
Elnaugh was known for her business career in the greetings-card industry, especially through the Red Letter Days brand. Her experience gave her a relevant perspective on consumer products, branding and retail, all of which are frequent subjects in entrepreneur pitches.
This fact concerns the original panel, not the programme's entire history. Deborah Meaden later joined the show, and other women including Kelly Hoppen and Sara Davies appeared in subsequent lineups. Confusing the original cast with later panels is the most common source of a different answer.