There is nothing in principle preventing your friend from making a successful application even if she is in reduced circumstances. What sometimes happens is that people will try to contrive something and that gets them in to trouble when they get caught (and then they blame it on lack of money).
The controlling reference is Paragraph V 4.3 of the rules, and most of these apply to you, the third party. If you do not think you can meet all of their requirements then you should advise your friend not to make an application at this time because something will go on her record which was your fault. Bad thing.
The most difficult hurdle will be establishing that your relationship is genuine. It means you met her before in real life and have an ongoing relationship that has endured for a while. If you didn't meet her in real life, then you should select a different country to meet her in before trying a UK application.
You would need to explain in a fairly detailed letter how you met her. If it was on a dating site, then list the site and the date you 'virtually' met and what you were doing that site. Then explain how you proceeded to get together in real life. Also, what you are doing to stay in touch. Evidence can be helpful, but they really do not want to see Skype logs or similar stuff. As examples, they like passport stamps and photos (max of 2 or 3) that are NOT selfies.
You'll need to submit your bank statements and employment contract and all of the other evidence that she is supposed to submit but cannot. She will have to explain her circumstances and why a visit is appropriate at this particular point in time. She also needs an abundance of "high quality" social and economic ties to Kenya.
Finally, if you are proposing to stay together (they like it better if you have stayed together previously), you should include your tenancy agreement or permission from your landlord that she can stay there. They will be minded to refuse otherwise.
Adding some generic advice about the British High Commission in Nairobi...
Nairobi isn't the worst issuing post on the Africa Desk, but it isn't the greatest either. The post was caught out fudging their performance stats and also losing people's documents. Make sure you send a self-addressed prepaid envelope and a request that your sensitive information is returned. Make sure your passport photo and visa(s) copies are certified by a solicitor. Send only original bank statements (not your own print outs).