Why is my girlfriends vagina suddenly so smelly? Thinking of dumping her for my other one

Help yourself too. You all need to be checked for stds. Some infections are not treatable. Unless ur ready to deal with that, use protection every time. Unless ur ok with ur girlfriends having other boyfriends, and ur sleeping with them too, and their partners, etc, be careful with your body and their hearts.
Help her! If you care about her, why don't you take her to the doctor so that she can get examined to see why that is happening? Maybe she has an infection. Maybe she caught something from you since you have another girlfriend (you may not even know you have an infection). Help the poor girl, man.