The cyst has remained the same size, but a smaller one has appeared under her ear and I am not sure what to do next. The vet has given the option of having a bi-opse to check and remove the larger cyst, but I would like somemore advice before putting her under anaesthetic.

Is it a cyst, or something else? You can't really biopsy a cyst, you generally just remove it.
Cysts can be drained, but they will continue to grow back unless they are removed surgically.

As far as I know the vet had diagnosed it as a cyst.

Is it very large? You can leave them if you wish but they can grow. Surgical removal will take out the stem of it, so it won't grow back.

Its about 1cm aand has not grown since, but a smaller one has appeared by her ear.