How long does it take for glucose levels to go up after an apparent episode of diabetic hypoglycemia?

I'm home alone with my grandmother who has type 2 diabetes and dementia.I haven't seen her have a episode of hypoglycemia in years but two days ago after I after I gave her a shower I sat her on the bed to go get her pajama and my mom noticed she had her head resting on her chest,like she had fallen asleep while sitting,she asked her why she was doing that and my grandma said she was just resting,I came back with the pajama and her head was once again sitting on her chest like she was asleep,I asked her if she was okay and she lifted her head and said she was but less than a minute later her head fell to the same position and we were talking to her but she wasn't making much sense.I ran to get the machine to measure her glucose levels and they were just 55 which is really low,we gave her sugar and she went back to normal,then my mother made some tea with cookies for her and everything was fine.Today my mother is doing the night shift and I'm alone with her,I admit I got a little distracted with a movie and the last time she ate was around lunch time,probably 1pm or earlier,it's now 4pm.She went to the bathroom and I was washing her hands when she started doing the same thing with her head,I asked her if she was okay and she said she was but then I noticed she reached for the sink to try to stay up and I immediately told her to sit down and ran to the kitchen to get some sugar,I then moved her to her bed,she was walking fine and I went to get everything I needed to measure her glucose levels,probably 5 minutes passed since she took the sugar to the time I measured her glucose levels and they were 136 which seems kinda normal,is it possible for glucose levels to go up so fast?I just gave her a spoon of sugar...