hi clj,
a psychiatrist can make recommendations, but they can never actually make you swallow a pill

. what i would personally do is bring up the weight gain concern and let your doctor decide what meds can help your main problems as well as avoid weight change. my doctor is very good at this - i've been on 13 meds and not one has made me increase weight - because he knows i'll stop them if i do gain weight. he also usually gives me a choice of maybe 2 or 3 that we could try, and lets me decide which one i would like to go with after i've done some research.
so whilst suggesting celexa can be good (it can lead to discussion about what has worked for your mum, why you are interested in it etc) i would encourage you to be open to your doctor's suggestions also. if he understands you worries about going on meds, then i am sure he will keep it in mind when making any recommendations

.