うれしがっちゃう
ureshigacchau

Godan Verb (ru)
Godan Verb (u)

The completive aspect (contracted form) - indicates completion or regret of 嬉しがる

1. To be happy (and show it excessively); To be overjoyed (and show it excessively); To become happy (often with a nuance of being carried away)

Completed Action
Colloquial