This is COMPLETELY normal and is a phase!
This phase is h*** o* grandparents! No matter how much you tell them it is
normal, it still is VERY hard for them. Imagine wanting to show your love and
cuddle with your sweet grandbaby and you are rejected, how hard that must be!
Thankfully, the phase will pass and your baby will soon be delighted to see her
doting grandparents. My older daughter can't get enough of her grandparents,
although she went through a phase around the same age your daughter did where
she only wanted Mommy and Daddy to hold her. Our younger one is, I believe,
just emerging from that phase (she's 7 1/2 months).
A few ideas...you could try putting your daughter down in a bouncer, on a
blanket, etc. and leave the room (with her in a happy mood of course). After
you're gone a few minutes, your parents could try picking her up. She might not
protest if you are not in sight. This allows your parents to get in some much
needed cuddle time! I have found with my girls in this phase, they cry more when they can see me and someone else is holding them.
Also, having a friend she sees often hold her for a few
seconds here and there could help her get used to the idea of other people
holding her.