Sentimental girl invited to see garden left home (7)
I believe the answer is:
maudlin
'sentimental' is the definition.
(I know that sentimental can be written as maudlin)
'girl invited to see garden left home' is the wordplay.
'girl invited to see garden' becomes 'Maud' ('Come into the garden, Maud' - Lord Tennyson).
'left' becomes 'l' (common abbreviation).
'home' becomes 'in' ('he's home' can mean 'he's in').
'maud'+'l'+'in'='MAUDLIN'
(Other definitions for maudlin that I've seen before include "Sentimentally tearful" , "Mushy and emotional" , "Effusively or insincerely emotional" , "Over-emotional" , "Self-pityingly" .)