Unlike many domestic relations cases (e.g. divorce, custody), there are no standard forms for adoptions in WA. Theoretically you could attempt to do it on your own if you are well-versed in the law, but I would not actually recommend that to anyone; at least consult with an attorney first to get a better understanding of what you would need to do. If you would like to read up about it before consulting with an attorney, the laws are found here: http://apps.leg.wa.gov/rcw/default.aspx?cite=26.33
You should also be aware that adopting her does not automatically mean that you would have legal custody of her children if something were to happen to her. Please read this publication about placement of minors in the case of parental death: http://www.legalvoice.org/pdf/self_help/Placement_of_Minor_Children.pdf
There are no standard forms ---each attorney creates their own form. If you are unable to do the same, you will need to hire counsel.
The information is for general information purposes only. Nothing stated above should be taken as legal advice for any individual case or situation.