I knew some people similar case like your partner.
Actually They most likely to look at her new application than the previous one BUT as long her supporting documents are really strong and genuine she will have a good chance of getting a visa.
And have a good reasons ready incase the ECO will ask her why she overstayed her visa and always tell the truth!
My friend overstayed her visa for almost 4 years but she was been issued a Spouse visa within 2 months without interview and now she's is happily living with her partner.
