Translation.

An Asian woman leaves the deli hand in hand with her black boyfriend, when suddenly, a beggar imposes on them.

Whats wrong with this sentence? Word claims that the grammar is wrong

[Mister Micawber]

Hard to tell-- be wary of sentence checks and spell checks: they are notoriously erratic. It is much better to rely on yourself, in the long run.

Probably the comma after 'suddenly' is wrong; I would certainly call it so.