My mum uses Android. I have already used the electrum wallet myself and actually found it quite good. Updating the latest Blocks take some time if you not use it daily but that should be totally okay. Also I don't find that UI from electrum very nice.
A feature that I miss is that if my mum does a transaction that is over a certain amount, it would be a very cool if I could "co-sign" it.
I think the way you could get around this (if you were using electrum or another wallet happy with multisig) is by making two accounts.
Say you have 0.1
BTC and you only want her to spend 0.01
BTC for daily use (without additional security) then you could make a secondary wallet with that amount and make a primary wallet with the greater amount in it. If you're worried about her getting scemmed then it might be better to do it that way as a scammer could just send a load of other addresses to her.
A lot of the time with electrum, she can sign the multisig transaction and then send a message with the sighnature (as it's automatically copied to the clipboard) and then you can sign it wherever you are as long as you have your phone and it's online.
I miss the old Blockchain.info wallet
What exactly do you miss about a particular wallet? That service still exists, the only thing that has changed is the domain name, before .info, now .com. Some things have probably changed for the better, and it's still a very popular online wallet, especially for beginners.
Personally I don't like the new ui of the block explorer, it's not as light to load as it used to be and the top banner isn't as nice. Haven't used the wallet in a long time (and barely ever used it before) but I imagine it's plastered with ads and ref links now...