。
She buys shoes compulsively.
Literal
[topic-は] indiscriminately shoes [object-を] buys.
やたらと here marks the buying as compulsive, excessive, or undiscriminating — the speaker is signaling that the volume or randomness of the shoe-buying is the noteworthy thing. The dictionary-form 買う as the main verb describes a habitual or characteristic behavior, much like English 'she buys' as a generalization rather than 'is buying' for one moment. A short, sharp character sketch.