Imaginative play is both normal and healthy for children (read "The Need for Pretend Play in Child Development", posted on Psychology Today, as just one of many sources that support this theory).
Young children regularly cuddle, talk to, and animate their toys. A handful of anecdotes:
- My son will sometimes have his favorite stuffed cat tell me that there is a problem ("Moppy wants you to know he's bored") rather than admit it himself.
- My daughter would act out scenes that seemed to be pretty obviously mimicking things from kindergarten; the most memorable was when the toy pots and pans decided to make fun of a toy plate for being friends with a toy fork.
- All three of my children play together, each holding a Lego figure and having them navigate the living room furniture, and speaking as their character as they adventure around the room.
Modeling this behavior yourself will not "make the baby believe cuddly bears talk back" (see below). If anything, it could help your child see that imaginative play is fun and normal. And as she grows and enacts her own imaginative, creative interactions with toys, engage in that with her; let her imagination take the lead, but interact with her through the toys.
However, if her mother is continually complaining about your imaginative interaction, I would also be concerned that normal, healthy play would be interpreted by your spouse as an abnormal development "caused" by your actions. Instead of allowing your daughter to play without concern or interference, she'll forbid or criticize it. Look into ways to resolve the difference between you and your spouse so that conflict can be avoided.
In your comment, you asked about whether it's possible for talking to the bear too frequently to be problematic. This is rather harder to answer and I have to rely on my opinion rather than research (I haven't read about this, really). However, I believe there are some ways of interacting with a toy that could model "unhealthy" imaginative play:
- Talking "with" the bear (e.g., pausing when it "responds", answering questions "asked") instead of talking "to" the bear.
- Talking to the bear more often than to your spouse, child, or other friends and family, or preferring to talk to the bear even when someone else is in the room
- Talking to the bear throughout the day
- Talking to the bear when it isn't physically present
I'm honestly not sure what the repercussions of that might be, but these all seem (subjectively) to exceed normal imaginative play even for children, and especially for adults.