young lady, do NOT let anyone take advantage of you like that again.
she first offered you $100, which says clearly that she knew it was worth at least that much. then she backs waaaaaaaaaaaay off to $75? Never, ever, ever ... and i say again ... NEVER let a client know you had no idea what to charge.
if you want your work to get the respect it deserves, YOU need to start respecting your work and yourself.
now toughen up, cookie, or we're going to have to take a stroll to the woodshed. (hmmmm ... no emoticon that fits. just picture me with my hands on my hips, wearing my sternest "mother loves you and this is for your own good" face. :wink: )