If her income is below 18,000 (or 36,000 if married) she may be exempt from DIRT when she reaches 65. This can affect things - if she is exempt from DIRT, the An Post savings bonds/certs (which are already not subject to DIRT for anyone) become less attractive. The figure of 4.61% that you quote for the bond is a "grossed up" figure for comparison purposes. If someone is exempt from DIRT they should use the figure 3.23% instead and compare it with the gross AER interest figures from bank accounts.
Also, regular saver accounts can't really be compared with fixed term lump sum deposits. With the former you can only lodge a set amount every month. Unless there is some clever drip feeding strategy using multiple accounts that I'm not aware of, those with a lump sum are better off with a fixed term deposit even if the interest rate appears lower.
Lets say you have a 12,000 lump sum and attracted by a high interest rates of 4%, lodge it in instalments of 1000 per month into a regular saver account. At the end of the year you won't earn 4% on 12,000 though - you only earn 4% on the first instalment. On the second instalment you earn 11/12th of 4%. On the third 10/12th of 4%. And so on. At the end of the year you will have earned approx 2% on your 12,000.