From a tax standpoint, you want the account in her name; so the income and capital gains will be taxable to her. I assume she is in a lower tax bracket than you.
If the account is in her name, the investments (appreciated stocks and mutual funds) will "step up" in cost basis when you inherit them.
These days, with internet investment trading, you can easily access her account for investment purposes. You may want to have her execute a power of attorney for you.
You should consider registering the account as Transfer on death (TOD). See https://www.nolo.com/legal-encyclopedia/avoid-probate-transfer-on-death-accounts-29544.html
