Someone can mean well and still need clearer limits around how they help.

Good intentions are not the same as a good fit, and saying so sounds like an accusation when it is really just a correction. Help that comes at the wrong time, in the wrong shape, or with too much of the helper attached still costs the person receiving it, however warmly it was offered.

Name the shape rather than the person: what is genuinely useful, what is not, and when it works best. Say it early, while the help is still occasional and nobody has built a routine around it.