1. Talk to people. At the very start of an agency business, you get clients by talking to people - at networking events, conferences, via LinkedIn, etc. You don't get those first clients by sharing stuff on socials or doing paid ads.
2. You'll never make money if you start with that negative assumption - "companies that are strapped for cash already". Companies have cash, otherwise they wouldn't be alive. You just need to be a valuable place for them to invest that cash.
3. When you first start out as an agency, you'll do a lot of underpriced jobs, say yes to lots of things and learn a lot, but not make much money. Later you'll learn how to say no more and make more money. Read Blair Enns' book "Win without Pitching".
Your customers want to get leads/traffic and convert them into sales, and you're promising you can make "marketing" that does this, so show them by creating that "marketing" that gets them in your front-door.
What do those small and medium businesses do, and how can you help them make more money? That's what they want to know you know before hiring you to help them with that.
Something to think about: Being good at B2B means you can get really good at B2B, but focusing on B2C customers means you still have to be good at B2B because of who you're selling to.
That being said, it can be easier to break into B2C... My thinking is B2C customers tend to have lower expectations perhaps because they don't have to (necessarily!) be good at B2B...
Second get results.
If your business is marketing, your starting point it the top 10 ad keywords on Google. If you aren't operating in this space, nobody is going to take you seriously and trust you with their ad budget except as an employee. And the best thing to do is focus on a specific industry and learn it inside and our. The auto sales market is already locked up between 4-5 people and the rehab space is full of criminals (like real felons doing real felonious shit that people will go to prison for someday.). The rest is where opportunity is.
But to reiterate my first point, your target companies have to have that ad budget to begin with.
/signed 5 years in legal marketing spending around $450M/120M traditional/digital per year.
Maybe it's not better for her to start working for a company to get her name in the street and connect with relevant players/customers first?
While you're at it, go right to the competition and make industry friends if you can. They can provide some of the best referrals you can get, but the old cutthroat competition trope usually has to be kept at bay while you build up a reputation.
Be humble, don't give up & good luck.