Are you sure it’s your sister and not someone else you want to “sell” something to? Just keeping an open mind about potential scenarios. Scammers often ask for advice to make it easier for them to explore options if for example their victims live in places where buying bitcoins is very restrictive such as New York. To make it easier to get that advice they will often say things like it’s someone in the family, a friend, brother etc who owes money.

If she is your sister, she can wire you the money or send it by Western Union or Moneygram. And if I assumed wrongly, then I apologize. I’m just being open minded about this because the last thing i would like to see happen is for scammers to get all the help they need to fleece victims.

If the story is as you posted above, you can help your sister create a wallet, preferably one with private keys under her or your control. She can then buy coins from one of Coinsource’s ATMs. Or she can search for advertisers on Localbitcoins trading in NJ or CT.

It would be easier for her to wire you the money and you buy the coins in Europe or on an exchange.

Don't use Coinbase as a wallet service. When looking for a bitcoin wallet, ALWAYS go with a wallet that allows you to hold onto and keep your own private keys.

For a hot wallet, I personally use GreenAddress (https://greenaddress.it/en/), as it is a SegWit-enabled wallet. This just means cheaper fees because of reduced transaction sizes. And it's fairly easy to set up and use on any device that you own. Just make sure to document and store your private key. If you lose it, you'll be shit out of luck when it comes to recovery.

Feel free to PM me or post here if you have any additional questions.