As long as your relationship has been genuine (it will be very helpful to keep all the proofs of relationship/cohabitation - emails, texts, call history, utility bills in both names, financial interdependencies, copy of her passport pages etc), you will be fine.
The PR you received is independent of your partner. Both you and your partner receive permanent residency upon having 5 years of residency. After that, there is no longer any requirement or dependency of being in the same relationship.
You should, however, send any changes of your relationship to INIS (e.g. separation or divorce). This will make sure that you abide by the law (which requires all non-EU nationals to report any change of address or relationship). You will still retain your Stamp 4EUFAM for life.
The question of divorce is not something this forum discusses. It’s best if you ask the embassy directly.