A question to ask is: is God not enough?
No matter how much I loved my dead human friend, a question to ask is: is God not enough? Why should I even care if I see my friend or family member again in Heaven in that case?
Of course God is enough, God is always enough, including here on earth. If I lived my entire life in a solitary confinement cell and never had a loving relationship with any creature on earth that whole time. God would still be enough. But He sends us loving friendships and relationships on earth, including with animals, as a way of showing us His love, and the idea that these earthly experiences just vaporize or cease to matter at all when we join ourselves to God does not seem to take into account the fact that God gave us the gift of the companion in the first place. It’s not an either-or where you choose between your dog and God. God’s love permeated the whole relationship you had with your pet because God created that animal and sent you the gift of its friendship on earth. Whether God allows you to keep experiencing that gift after death or has another plan is up to Him.
I realize many people on here seem to really like the idea of a Heaven where all we do is sit and focus on God all day and no experience, relationship or loving bond we ever had on earth matters any more, but to me and probably to other people reading, that idea of Heaven sounds about as pleasant as a lobotomy, and I also don’t think God means to just erase from our consciousness every bond we had on earth or he would not let us experience such bonds in such a deep and meaningful way.