S.H.
If I were you I would opt for 3 days a week, that way your daughter will feel more involved and connected to her new sibling, and won't feel pushed away and replaced with the new baby. I have a 3 year old and 5 year old, and I still only send my 5 year old 3 days a week. She and her little brother are very close since they spend lots of time together, and I know it won't be long until she'll HAVE to be gone 5 days a week, so I want this time now. You'll never get this time with her back!