God experiences time differently. All simultaneously rather than the chronology of man. How this works out for the second Person of the Trinity, Who is both God and Man, is a great mystery, but it is interesting to note that Jesus' speech to Simon appears to indicate the cause of the woman's great love happens after the effect, namely God's forgivenness.
So, for the woman, her great love for Jesus led her to do what ever she could to adore Him. It is extremely unlikely that she expected anything; those at the table were astonished when he told her her sins were forgiven- so it is quite likely she was surprised as well. She merely sought to worship, to encounter God. I do not, of course, suggest that she had some sort of coherent theology. She was probably quite incoherent, but she had love.
Vertigo. An appropriate sensation when contemplating the ineffable God.