Dog 3 weeks possibly pregnant.?

Im watching my aunts baby for a couple days while she is visiting her mother-in-law in the hospital. But any ways my aunt is a breeder of 32 years, this is her last litter. Roma is a 3 year old English springer spaniel and she was breed approx 24 days ago. The stud Ripley has a champion title in show, and was hand chosen. That's just some background information. My question is that can dogs develop at three weeks? Like I've noticed that she's had flab's under her . What else can you notice at three weeks? She is getting picky about her food here lately also. If you guys can't answer me that's fine, I can just ask my aunt when she gets back, but I just don't want to bug her while shes at the hospital. Don't leave unnecessary comments, my aunt is a breeder of 32 years and Im sure she knows what shes doing thanks.