May be she will be there tonight.
Maybe she will be there tonight.
Maybe is one word and means ‘perhaps’. It normally goes at the beginning of a sentence: ‘Maybe she’s at home.’
May be consists of the modal verb may and the verb be. It comes after the subject: ‘She may be at home.’
Compare: ‘Maybe she is tired.’ ‘She may be tired.’
Check our grammar lesson on the difference between maybe and may be.