I am frequently asked on my courses what to do if someone doesn't want your help. It's an incredibly frustrating thought that you can see someone is struggling or in distress, and yet they are refusing help. This even more upsetting when that person is someone you are close to or love.
As tough as this is, we as would-be helpers have to face and accept, that our help can and very often will, be rejected. If you put yourself in the shoes of the other person, it could be that they don't realise that they need some help: we are very often brought up to believe that we should be able to cope with everything life throws at us.
Therefore useful tactics here would be to have the expectation that you might get knocked back, but know that if you plant the seed that help is possible and you are there for them; that could eventually be the catalyst for change.