No, rental income isn't assessed in the same way as income from employment, so the various disregards that you read don't apply.
If she didn't let the property having let it in the past, it could be seen as depriving herself of an income in order to get a SW payment, and an assessment could be made anyway, so that's not of much benefit to her.
One point to note is that if she does get Disability Allowance, she will start to get credited PRSI contributions, which may allow her to qualify for Invalidity Pension in the future (some posters here have done that). If she qualifies for Invalidity Pension, the means assessment on the rental income would then not apply.