Question about etiquette with recruiters

So I contacted a recruiter late last year and she said she'd keep me in mind for a role that she is now recruiting for. She has asked me to attend an assessment centre next week. I got her call today, yet to call her back. However this morning I also recieved another email invitation for another interview in two weeks time for a different role.

What is the proper etiquette here? Should I tell the recruiter about it or no need? Say I get both jobs (highly unlikely), is it okay if I reject the one the recruiter contacted me about or is that poor form??

New to all this, don't know what to do.

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