1 A lovely lady rode him fair beside,

lovely > lovely; loving; lovable [by virtue of her admirable qualities] fair > fittingly, becomingly; skilfully

2 Upon a lowly ass more white than snow, 3 Yet she much whiter; but the same did hide

the same > [her complexion she]

4 Under a veil, that wimpled was full low;

wimpled > {Falling in folds} full > very, exceedingly

5 And over all a black stole she did throw,

stole > robe

6 As one that inly mourned: so was she sad,

inly > inwardly