Yes.
If it's with same provider, my understanding is that it can piggy-back on the same direct debit mandate that's set up for the main scheme. Maybe under a separate policy number, but that's fine.
If it's with a different provider, she could ask employer to set up a new direct debit from company for second provider. Employer isn't obliged to do this but I think they'd find it hard to refuse when she explains that it will save her (up to) €300 per annum as shes doing it execution only.
TBH, paying from her own account and then sending the PRSA Certificate to Revenue isn't such a big deal. They'll adjust her tax credits and notify employer so she'll see it in her payslip fairly pronto. There's a bit of admin in it if she changes the contribution levels on a regular basis, but still....it's well worth it.