tl;dr
All popular frameworks are at par as far as feature set, documentation, and community support are concerned. So it doesn't matter what your friend starts with. Understanding core concepts of frontend engineering is more important IMO than learning a framework.
Long version
Depends on the objective of learning a frontend framework. If securing a job is the objective, then it makes sense to go over contemporary hiring dynamics and choose the one with the most job listings in the learner's context (E.g. React may be the most popular worldwide, but Vue might be popular more than React in a particular domain that the learner is interested in working). If it's an exploratory learning activity, then I think all popular frameworks are at par with feature set and documentation as well as community support for troubleshooting. I get this question asked very often, and I usually recommend people to invest a week each in exploring popular frameworks to cover breadth, and then based on comfort and priorities such as job or an upcoming project, decide which one to go deeper in. It entirely depends on the comfort and developer ecosystem around the learner then. Another objective could be to be adventurous, bleed on the edge, and work on something that does not have an ecosystem around. In that case, one could choose the least popular framework and contribute towards making it better.