I don't think you have any reason to think she won't return the deposit.
I imagine you didn't sign a contract as you now say she isn't a proper breeder. However, unless she is a con artist, she will probably give you the money back.
There are 2 separate issues here - should she let you have the puppy when there will soon be a newborn
And
Will she return your money?
Re the first, it really will be up to her. No-one has to sell a puppy to someone they don't want to - you have no entitlement to buy. It would have been better if she decided before taking the deposit, but given you didn't mention the baby, there was no opportunity to make that judgement.
Many people think a newborn and puppy are a bad idea - therefore her attitude shouldn't be surprising really. It is a bit odd that you didn't mention your pregnancy.
Re the second issue...you will be very unlikely if she now keeps your deposit and you have to go to court to get it back. However, it really is too soon to think this has happened.
To be honest, you haven't dealt with this very well Op. You have dealt with someone who isn't a proper breeder, plus you didn't reveal a crucial detail about your set-up. Would you have kept that info from a proper breeder? I expect their contracts state the contract is only valid if full disclosure is given about the set-up the dog is going to. You not revealing your pregnancy would make the contract void. Your willingness to deal with a non dog breeder and not reveal crucial details doesn't make you come across as a totally responsible dog owner. Your sound offended at being crititicised and caught being not totally honest, rather than genuinely concerned about what might be best for the puppy. Okay, the way the breeder spoke to you might not have been professional and a bit patronising, but given your failure to reveal your pregnancy it can hardly be surprising.
Perhaps the best thing would be for them to return your deposit and you to think again about the whole thing....consider why breeders say no to pregnant people and those with small babies and perhaps delay your purchase.
And next time, don't try to do it on the cheap but go to a proper breeder. I'm sure your family can have a dog and thoroughly enjoy it....but just take a step back and think about the timing.