I would skip the ice cream, especially if she needs to lose weight. Carrying extra weight makes collapsed trachea even harder on a dog.
A lot of people will give their dogs licks of vanilla ice cream, but I worry what ingredients are really in a lot of ice creams. The risk of sugar substitutes concerns me. Even if it is real sugar, dogs don't need it (I would like to cut down the amount of refined sugar I consume too
).
Plain yogurt is okay for most Yorkies, but can be fattening if fed too much. Be sure to factor it in when calculating your dog's daily intake of food. I used to give my 9 pound boys 1/4 teaspoon a day of plain Greek yogurt. We stopped because I have to watch Max's weight.