There are some small things about the signature which would cause me to approach it with caution, but there are others much more learned on her signature here then me so I would wait for additional feedback. The photo is definitely too vague to show what is being signed so I would not take that as provenance on the specific piece. Either the graph stands on its own merit or additional provenance details would need to be supplied, The picture is just too vague to add any provenance value, imho.