Since you're talking about how she looked before the surgery, it stands to reason that all this (the way she looked and her lip surgery) was in the past. So, I'd say go for the past-tense verbs for the entire sentence, though This is her original look before she underwent lip surgery is certainly possible. The only problem with it is that it just sounds a little bit clumsy.
And please remember that with third-person singular subjects you should always use third-person singular verbs. What's the third-person singular form of the verb to undergo? It's undergoes and not undergo or undergone. Take a look at this little chart if you tend to forget that (that's all the forms English verbs can ever take):
infinitive: to undergo She is to undergo lip surgery.
bare infinitive: undergo She will undergo lip surgery next year.
third-person singular: undergoes She undergoes lip surgery every year.
past simple: underwent She underwent lip surgery yesterday.
past participle: undergone She has undergone lip surgery two times in her
present participle: undergoing She is undergoing lip surgery. The surgeons
are working on her lips right now.
But if I were you, I would rewrite your sentence completely:
This is how she looked before she underwent lip surgery.
Possibly, an even better way to say that would be this:
This is how she looked before her/the lip surgery.