Too much wet food?

[Alissa]

My cat is 17 years old now. She began getting wet food every night because I started mixing some arthritis medicine into it. Not long after she stopped really eating her dry food. She started losing a lot of weight then. Recently she's started crying for more wet food when we even go NEAR the refrigerator. At 80 years old, I figure if she wants to eat "ice cream" she can eat "ice cream." It's only been a few days now, but it looks like she may already be gaining weight and going to the bathroom better (she's had problems with that in the past). My question: Do I need need to monitor her wet food intake? Are there any repercussions to her eating too MUCH wet food. She has not been throwing up or anything along those lines, but is she missing out on some certain nutritional requirements eating only wet food?