Hi Private User, you are very astute to be suspicious. As a saga figure Aslaug's existence definitely falls into a grey zone between fact and myth. This issue has been discussed often in thread's started from Ragnar's profile.
The short answer is "probably not", for more context read this comment https://www.geni.com/discussions/129645?msg=904068
The link in the following comment is also very good and if you can be bothered reading all 26 pages of that thread you will learn more than enough about the topic to put anyone you meet at a dinner party to sleep :)