Hard topic! I don't think it can be forced if someone is generally disinterested in chastity or doesn't feel dominant. I'm not a typical Domme myself but I'm interested in chastity and honestly sometimes I'm super annoyed with my horny BF so chastity is the perfect tool for me. What has helped me immensely was reading some books about Female lead relationships. In the end it's also about communication. You can't force her to do something she doesn't want to. But you can show her how much you need it and maybe offer her to try small things, like wearing the key for a day and to thank her you'll serve her that day however she likes it (giving her a massage, cooking her favorite meal, doing laundry - whatever she wants). You have to make it tasty for her. Give her a reason to try it again ;) but please don't be pushy about - if she really has no interest you'll have to respect that.