A woman turning 50 is experiencing new things in life and finding new hobbies she likes to do, so give her gifts that encourage this. She is also still juggling a career, family or both so she needs the chance to relax, which is another gift you can gift her. Each woman is different so decide what to get her based on what her life is like.
When a woman is turning 50, her taste in clothes may start to change, and she would appreciate the gift of new clothes. If she is picky, or you do not know what size she is, then get her a gift token to a store so she can go and pick out her own clothes. If you do give her an outfit, give her the gift receipt as well so she can exchange it if it does not fit.
At 50 she might be still working and probably has a lot of family responsibilities as well, so a weekend away will be a very welcome gift. Get reservations for her at a nearby resort or tickets for a cruise (if she lives near a port). All-inclusive trips are great because she doesn't have to pay for anything. Consider going in on this gift with a few friends and family members.
Give her a certificate to have a spa day. This gives her the chance to relax and get away from life for a while. You can get a package with services included that ends up saving money on more treatments a lot of the time, or you can give her a certificate and let her choose which she wants. Choose a spa close to where she lives so that she doesn't have to drive too far to enjoy her gift.
As women get older, they may start adopting new hobbies, so get her a gift that embraces these activities. For example, if she has recently taken up hiking or scuba diving, then get her equipment she needs for that, like hiking boots or a mask and snorkel. Ask her subtle questions about her hobbies so that she doesn't know you are asking with the intent of buying her something. If you don't know what to get, then give her a gift card to a store that sells things for her hobby.