Hi, as you have mentioned that your mom does not have any health issues and is only trying to keep her weight in check, i would suggest that she focuses mostly on having healthier meals...she can easily maintain her weight by including whole grains,fresh and seasonal vegetable and fruits, pulses etc.
Coming to your main question which is if she can have apple cider veniger...Acv is generally safe for consumption but i would not suggest for her to have on a regular basis...if at all she wants to have it...she may take it once or twice a week one table spoon mixed in a glass of cold or luke warm water after lunch or dinner.
Regards,
Dt.syeda.
Next Steps
let me know in case of any furthur queries
Health Tips
i would also recommend her to have a regular walking routine which will be very good for her over all health