It’s very difficult to say. It will only look fatter than normal about 2 days before giving birth. She can build a nest or improve the existing one and will usually be more active than normal. Dwarf hamsters are pregnant for about 19-21 days (Syrians only 16 days) so the best thing you can do is wait and see. When they give birth, you can check our You Tube channel “Everything about your pet” on what to do in these cases, but above all remember not to touch the young.