What to do with annuity payments as 68 yr old?

My 68 year old mother started receiving annuity payments of ~$5k/month, she’ll get these payments for ~5 years.

She can afford her day to day life from her pension and social security so I was going to setup a taxable brokerage account for her. My thought was to dump most (all?) of her monthly annuity payments into VTI and maybe some BND.

Any reason why those would not be good choices for investments? I’m mostly wondering because most stuff I read about is catered to younger people still in the workforce, not sure how her age would factor into stocks vs. bonds.