Peace be upon you. According to Grand Ayatollah Khamenei and Grand Ayatollah Sistani, leaving one's homeland with the intention of not returning, or having certainty that returning is not possible, constitutes a departure from that homeland. Simply moving to another city does not necessarily mean one has abandoned their original home. If she intends not to reside in Beirut at all, she should pray shortened prayers (Qasr); otherwise, she continues to pray in full (Tamam). May you be successful in all good.