As far as I am aware she would need to apply for the HK book from her home, best thing is to ask some local travel agents. Even with the book she might not be able to get a visa allowing her to fly to HK directly, instead there are several avenues by boat that local operators in Shenzen use, either have her go online and look it up or again go to a local travel agent. Originally only Beijing, Shanghai and Xiamen were on the list, but Shenzhen should be added this year...http://www.mac.gov.tw/ct.asp?xItem=101900&ctNode=6256&mp=3
. You can try contacting the mainland affairs council on that website, I would suggest she try as an individual tourist rather than mentioning her link to you and Taiwan. All of this would only get a short trip though, as before, I doubt she can live in Taiwan unless you are married and you have an ARC, but you can ask them.