Yes, on five occasions.
Jenny Campbell's personal website lists the following five investments: drinks brand Didsbury Gin, loyalty scheme ParkingPerx, truck advertising firm DrivenMedia, energy switching service Look After My Bills, and hemp skincare producer Carun UK.
All five of these investments were made on Dragon's Den, and as the site does not list any further investments, I find it reasonable to assume these were the only investments she made on the show.
The website itself confirms the Didsbury Gin investment, this Business Live article confirms the ParkingPerx investment, and multiple sources (including her Wikipedia entry and this Metro article) confirm the other three investments. Incidentally, her Wikipedia entry also notes the reputation you mentioned her having:
She built up a reputation of not making an investment in any business on the show, despite eventually investing in hemp skincare producer Carun UK, truck advertising firm Driven Media and also investing in energy switching service Look After My Bills.
(As a final aside, Campbell has since sold her shares in Look After My Bills and Carun.)