I still can't see what the judges saw in her. She was good, but I wouldn't say she was the best in her year (Tom, Austin and Rachel were better). Nor would I say series 6 was a particularly strong year - series 5 and 8, for me, are much stronger years in terms of female talent; I'd suggest series 10 and 11 are stronger years as well. I'd say (off the top of my head) that Alesha, Kelly, Gabby, Kara, Pamela, Denise, Kimberley and Natalie are all stronger dancers than Lisa. I'm not sure Lisa even comes into my 'Top 10' female contestants.
What sums up the (to me) farcical way the judges wet themselves over Lisa in series 6 actually lies in series 7. All of the series 6 Top 4 returned during series 7 - Tom returned to reprise his showdance in the first episode of series 7; Austin performed with Erin (and the other professionals) when the cast of Hairspray were the musical guests; and Rachel and Lisa did a guest slot in the final, performing (respectively) a tango and a something to Sisters Are Doing It For Themselves.
Tom, Austin and Rachel were as good, if not better, than in series 6 (Tom and Austin seemed more relaxed, maybe because they didn't have the pressure of competing; Rachel was scarily precise and sharp, as sharp if not sharper than she was in he Argentine Tango).
Lisa was quite possibly drunk.