Over 50 work in germany

[mariap]

Does anyone know a site, institution or advice centre in Germany (Frankfurt) where I can send my mother-in-law. She has lost her job 3 years ago and since then she's working as a carer in an old people's home. She is being bad treated by other members of staff and has to work obscene long hours and shifts even on her free days. As the place is private, they get away with it becasue they know she needs the job but honestly, I want her to get out of there. I've been searching all day for sites like "gumtree" here in UK which help people finding work.
I am aware of the age discrimnitations in Germany, but any help or advice you could give me would be very much appreciated. Thanks.