Dry throat sweating dizy. Else?

My mother (60 years) for last few days feel very dry throat all day and in night also she feel so dry throat that she need to get up and drink water couple of times. Today she suddenly got sweating and dizziness. After checking in a near by small clinic the bp is high and blood sugar in limit. As per her medical history she never had high bp but she had low bp sometimes and took coffee. No medication going on and she was diagnosed pre diabetic a month back (fasting 110, post prandial 167). She says she feels weakness also for a few days. Kindly guide what these symptoms means ? is this all because of high bp if yes how can some one suddenly get it if she never got high bp but low bp only. Or can this be due to something else ?