If you are out clubbing, and you see someone with whom you would like to dance, and lo, she is boogeying most righteously, more power to the both of you.
If you see that in addition to her righteous boogeying, she is incorporating the use of a cane, hey, there is a noble history of the use of canes in dance, from tap to Egyptian dance. Even though her cane looks more like it came from Walgreen's than any sort of dance supply establishment.
You may even be so bold as to take her free hand, if it's the sort of establishment where one touches one's fellow dancers, and she does not seem opposed to the concept.
One does not grab the hand with the cane.
One does not lift the hand with the cane from where it's been keeping the cane in fairly close contact with the floor.
Yea, even though she may be boogeying most fucking righteously, do not make the mistake of assuming that because the cane is not actively holding her up all of the time and she is stepping about in a sprightly fashion, that she does not actually need that cane for things like keeping her balance, catching herself in the event of sudden knee pain from a misstep, and the occasional bit of active-holding-up as she burns through her stamina.
Dancing like crazy with a cane and complete confidence is, after all, a much better option for her than hobbling around caneless and being stymied by stairs, and fearing to walk further than a block in case her knees should betray her. This is, after all, the weekend club scene in the city, and who the fuck willingly drives in San Francisco when there are other options?
One does not repeatedly yank the hand with the cane around.
One does not engage in an arm-wrestling match for control of where her hand (with the cane) is.
Even though she might not have immediately slapped you silly, this is still not okay. She might have been too shocked and appalled, and too unwilling to start shit on the dance floor when she was having fucking fun and out actually dancing for the first time in fucking years, and the first time with a cane, in celebration of her increased mobility.
In fact, this may be the first time that she's ever had to deal with someone being an appalling creep about the goddamn cane, and she may not be used to setting boundaries like that, because it's never come up before.
Because the vast majority of people are not drunk as fuck assholes who arm-wrestle you for control of your fucking cane, you idiot.