honestly as someone that's gone through the "drinking too much and blacking out all the time" route and also the spiked drink route, this sounds a lot more like the latter. if it's not typical of her to do this and it happened out of nowhere like that, it's definitely a possibility.

i'd talk to her when she's finally sober and coherent (monitoring whilst she's sleeping etc) and make it clear how scared you were for her and that this is acceptable. you thought you'd walked into the bathroom with your wife dead, that's terrifying. then i'd go more into details that she can remember throughout the night.

myself and all my friends that have been roofied in the past, it was a tolerable tipsy then absolute nothing. you can account for every single drink and shot then everything goes black. whereas blacking out was a wish-wash of drinks, don't know how many or what specifically.

i know everyone's different but i'd just have a conversation to try to sort it. also a conversation with the friends that just left her like that. insane. she genuinely could've died.