、。
I don't think I can win her favor as well as you can.
Literal
I [topic-は], you [degree-ほど] her [of-の] favor [topic-は] gain-seem-not.
ほど here marks an extent comparison — 'to the extent of you, as much as you.' With a following negative, the pattern [A] は [B] ほど...ない means 'A is not as... as B.' 好意 ('favor, goodwill') is the object being sought. えられそうにない layers several grammar points: え (potential stem) + られる (potential) + そうに (evidentiality) + ない (negation) = 'doesn't seem [I] can gain.'