From Miriam Webster online:
Giggling abounds in romance. Why? I have no idea. The majority of adult romance out there equates to mature characters falling in love, old enough to have sexual relations.
Every word that you use in your story is going to establish voice, and with giggling, characterization. If you have a character giggling all the time, what does that tell the reader? That (usually) the girl is a bit naive, a bit child-like. We may also have connotations that we associate with giggling from our past – teenagers, high school, silly blondes. I’m not bashing blondes, but they’ve been used in that context for so long, we automatically see it when it comes to giggling.
Is that who you want your character to be? Or is she a strong, independent woman? Maybe she is shy and timid and you can use that giggle appropriately, but either way, her actions need to match her character.
When editing, I allow giggling to pass more often in the Young Adult genre, but it’s well overused in adult romance. Challenge of the day: Let those women laugh!