Question

my dog has started eating very little. we have tried changing food, adding a bit of veg oil to her food (she licks up alll the oil but leaves the dry food) and even a bit of water to soften the food. She will only eat if the food is fairly soft and I am with her (or feeding her). We give her food twice a day and have tried leaving the food out for only 30 min and then taking it away (to train her that she needs to eat at meal times) but this did not cause her to eat any more. She's eating only around 40-60grams of dry dog food a day (she's a 7month old cocker spaniel). I'm worried about her. I tried looking at her gums and they seem a bit burple? What could this mean? Her heart beat also seems fast but she is a puppy and it has been fast ever since we got her. She is also still very playful and runs around the park like crazy (doesn't seem to be a lack of energy even tough she eats little and is very thin. She also can chew her bone for a long time so it doesn't seem to be a sensitive teeth issue. What can we do? I want to take her to the vet by my wife says that she is just being fussy about her food and tat there is nothing wrong with it. I'm really worried about her!