I think that poster was meaning that if @Muddle200 gets a full state pension of £11,502 then it will almost entirely use up her personal tax allowance of £12,570 - so if this £1500 a month is pension income, then a large percentage of it will be taxed.
Even if she has no state pension at all (very unlikely) then £1500 a month annualised at £18,000 takes her over the personal allowance, so she’d still lose some of it to tax.
However, I’m not convinced that the £1500 a month is pension income. I hope @Muddle200 comes back and clarifies, so she can get more useful advice. I’ve got a feeling from other threads that she may have come into some money, and that £1500 is to be withdrawn from savings. Really hope she can give us more info.