。
She's always complaining about how I do things.
Literal
She [topic-は] my way-of-doing [to-に] always complaints [only-ばかり] says.
やり方 ('way of doing, method, manner') is the い-stem 連用形 of やる ('to do') + 方 (a noun-forming suffix meaning 'way of'). This 方 suffix is broadly productive — 食べ方 (way of eating), 書き方 (way of writing), 行き方 (way of going), and so on — and is one of the easiest noun-formers in Japanese. ~ばかり ('only, nothing but') stacked onto 文句 ('complaints') and 言う ('say') gives '(she) does nothing but complain' — a very common way to express habitual unwelcome behavior. The に marks the target of complaint.