Give her time, anonymous. New catches are very much like new people you’ve met. Sometimes, they’re very eager to be your friend and the friend of all your friends; other times, it takes a lot of work and effort to get them to open up to you.
With that having been said, her integration should start with you. Give her every reason to trust you by treating her with kindness and patience. Don’t force her to do anything but make it clear (through both affection and verbal communication) that if she ever needs or wants anything, she can rely on you. Once she begins to understand that point, introduce her to your closest and calmest pokémon and have them befriend her and nurture their own bonds with her. (I would suggest beginning with one pokémon and allowing that pokémon to help you introduce her to a second, then a third, and so forth. Introducing her to multiple pokémon at once may overwhelm her.) Explain to your other pokémon that your pumpkaboo has a more timid disposition so they know how to approach and support her, and once she begins to trust them, allow them to introduce her to the rest of your day care.
In other words, take things slow and give her plenty of kindness, patience, and space as she needs. You’ll know when she’s ready to meet someone else when she grows comfortable being around you or the pokémon you introduce her to. But above all else, avoid being too aggressive with your attempts to befriend her, and never force her to meet any of your pokémon, as doing either may be perceived as a threat. Make sure she feels safe by speaking to her gently and letting her decide whether or not she’s ready to meet another member of your family.
Best of luck, anonymous!
The Pokédex According to Bill 