、。
She's very good at tennis, but I'm just as good.
Literal
She [topic-は] tennis [subject-が] very skilled [but-が], I [also-も] same degree skilled.
同じ位 (onaji-kurai, 'about the same, the same degree') uses 位 (the casual form of 位/くらい/ぐらい, 'extent') as a degree marker. 位 typically attaches to numbers or to 同じ to express rough equivalence — 三人位 ('about three people'), 同じ位 ('about the same'). The clause-final が ('but') sets up the contrast between the two skill levels. Note also the も on 私 reinforcing the parity — 'I also [am at that level].' All in all, a confident self-comparison with mild, polite hedging.