Doesn't matter best onboard there is for people like this. Instant money, green check. If she actually uses it you can get her on something on chain and show her how to transfer. Lighting is for about the amount you'd carry in cash, until she has more it doesn't really matter how, just that.

Phoenix or muun, but for starters is good WOS.

WoS is a good start. In addition to Phoenix and Muun, BlueWallet is another good option and has on chain and lightning. Lightning is custodial by default but has the option of non-custodial if used with your own node.