Bearpaw
Some V's just love to fetch from day one. Others, not so much. Unfortunately the time to really kick that desire into high gear is when they are puppies. Even them, it's no guarantee.
Your options are to;
1.) Find an object she likes to go after. maybe the Tennis ball isn't doing it for her.
"Chuckit, a toy company, has a frisbee looking toy that looks like a squirrel. My dog, that I got as an adult, loves that thing and will chase it all day long. They also make a nice plush ball that can be scented with quail, and a cool little frisbee. These toys are quitr a bit more animated than a ball.
2.) Have her "Forced Trained" to retrieve. If you don't actually intend to hunt her, I wouldn't do this. It's not worth it to put a dog through this just to chase a ball.
I have noticed a few things through the years with regards to V's and fetching.
Some V's naturally "look up" and others tend to look in a more horizontal plane. The ones that look up, I believe, have a greater natural tendency to track and mark an object thrown in an arc, and make a better "natural retriever". The ones that don't look up tend to lose the object once it's in the air and don't know what to do, or they just want to chase the object.
I have one right now, Tika, That loves to play fetch, but she is truly awful at tracking/marking a thrown object. It's not all her fault though, she got started late, and didn't actually begin any training of any type until almost 2 years old.
I've been progressively working with her by starting out throwing the object along the ground, and then progressively higher. When I know I'm throwing above where she wants to look, I throw the object a shorter distance so that it make a "plop" to draw her attention. Hopefully she learns to look up more. I use frisbee's and heavier balls that make more noise to help her out.
Gunnr chases anything thrown, and has excellent, natural tracking/marking instincts.
Both dogs didn't get introduced to water until last fall. Gunnr was about 15 months old and Tika 2 1/2years old. I got them both as adults, but not a rescue situation, so I pretty much knew what they had and had not been introduced to.
This spring I actually put on fishing waders, put them on a leash and took them to an area that I could "walk" them in the water swimming. If you do this, make sure that as you "walk" them that they can touch the bottom at times. The other trick is to have someone with you on shore, and each time you let them swim to shore they get lots of attention,and maybe a towel rub.
Don't overwhelm them. keep each individual "walk/swim"session short and do it multiple times in a given session to instill in them that: They are safe, they can get back to shore, you can be trusted.