Reportedly she wanted commitment from Jagger in the form of marriage and a baby and he wouldn’t marry her and give her a kid. He is known to not want to marry and made it clear, but she hung on. She reportedly neglected her business and spent almost all of her time following his band around. So she did not work on her career and it started to go under.
It’s too bad since she did have beautiful designs.
Do you really think she killed herself because he wouldn’t marry her? Remember, Jagger is the guy who went through a marriage to his last consort in Indonesia, then claimed later that it was intentionally invalid. She had about as much chance of marrying him as she had of marrying Liberace. And she wasn’t a new babe in the woods when she took up with him. Most likely she was bipolar or had a condition like that.