A: It's certainly possible. Any change in a child's daily routine can affect her sleep habits, including saying good-bye to Grandma and Grandpa after an extended visit. The best way to get your child back on track is to stick to your standby bedtime rules and rituals. Trying to find a new, magic solution will just confuse things more. After enduring your parents' departure your daughter will probably be comforted by your consistency and fall back into her old routine fairly quickly. During the day, talk with her about missing her grandparents and validate her feelings by telling her that you miss them too. Show her pictures taken during their visit (maybe she'd like one displayed in a frame in her room) and let her talk to them on the phone or send cards and drawings she creates just for them.
In the meantime, deal with your toddler's night waking with this gentle sleep training technique. When your daughter wakes up at night go check on her, but make the interaction totally boring. This means no lying down with her, talking, cuddling, or playing (don't allow her out of bed or pick her up if she's still in a crib). If she leaves her room, walk her back without a word or making eye contact. Eventually (in about a week or two) she'll get the message that she needs to soothe herself back to sleep the way she used to before Grandma and Grandpa visited.