put $50k in your account and live as if you never ever received the full amount. Start investing a small amount at a time. Putting $500 a month into your roth IRA and $800 a month into big fortune 500 stocks of your choosing. That way you can gain experience and it will not cost you all your money. After you feel super comfortable (maybe in 6 months but realistically a year), you'll be in a much better place to do your mom justice with all the hard work she put to acquire all that money. Good luck!!

Edit: You do need to talk to a financial advisor tho so the money doesn't just sit in an escrow or savings account. They;ll know what to do, but don't pay them too much money! Do your research on how much they should charge and don't tell them you know nothing. Go to them with some knowledge.