Taking Celexa And Buspar For Progressive Dementia. Worried About Interaction Of Drugs

HI! My mother is 89 and has progressive dementia. She gets around well but her memory is getting increasingly worse and with Namenda she got worse postural hypotension and fell. She is now on Celexa 10 mg. per day and Buspar 5 mg. per day. She was on the Buspar TID, but was getting very shakey and anxious in the evenings, so we reduced the dosage of Buspar to BID which she takes with breakfast and supper. She is seeming to be more anxious and shakey, sometimes tearful in the evenings with the reduction in the Buspar dosage. She has been on the Celexa for a month now. I am worried about the interaction of the two drugs, but we are reluctant to try something like Ativan because of the postural hypotension. She seems a little dizzy at times now, but not bad, mostly just anxious and shakey. Any suggestions?