She also acts as an advocate for working mothers as a director of Professionelle, a group dedicated to advancing women's careers through all stages of working life.
As a mother of three girls (Ophelia, 10, Georgiana, 8, and Matilda, 5), Muller knows only too well the demands of working motherhood.
While she says there is raised awareness around working mums, she doesn't feel that the workplace has changed proportionately to the "noise" that has been made around it.
"There is more awareness of the reality of life as a working mother, and there are pockets of workplaces which have excellent policies in place around this, but in general the situation hasn't changed that much."
Muller became aware of the difficulties of being a working mother when she was pregnant with her first baby. She says that a number of other women in her office were pregnant at the same time, and many felt unsure of their futures.
"I decided that I would like to focus my work on women in transition when I returned to working life," she says. "It can be very hard for women to make this transition."
Women who have worked hard to forge great careers often feel pressure to get back to work quickly after a child. It can be hard to make up lost ground even with a short time away.
"If you are a career-focused person, the reality is that the longer you are away from work, the harder it is to catch up where you left off."
She returned to work herself, on average, five months after giving birth. She says it was a difficult process, especially after her first child.
"When I returned to work after having my first baby I had a real sense of being responsible in a way that I'd never been before. I questioned if I was doing the right thing, there was a constant worry about not being present for the children when they needed me."
By the time she had her second child, she had found work in an office that she describes as "flexible and supportive".
This meant that she was able to spend more time with her baby while attending to her working requirements.
"The guys I worked with were amazing," she says. "I could bring Georgiana into work with me if I needed; it was a really flexible working environment."
Muller feels that this flexibility is a key to success of a working mother's experience.
She says that "output" is more important that "input"; and that if people are achieving their targets, managers should be able to offer them more workplace flexibility.
As an independent contractor, Muller has possibly experienced fewer difficulties than most. But she says she did lose potential clients when she was pregnant. "People have chosen not to use me for contact work as they want continuity and I wasn't able to offer that as I would be taking time off."
But during the course of her career helping professional women navigate the change necessitated by pregnancy and motherhood, she has encountered some shocking attitudes from managers.
"One woman I worked with announced she was pregnant with her second child. Her boss responded by saying 'that's just f***ing bad timing, you're headed down the path to career suicide'."
She says it's also not uncommon for women to be made redundant while on maternity leave and unable to fight for their roles.
But it's not all bad. She says there are pockets of "good news" stories as well.
"One expectant mother I worked with was encouraged to apply for a more senior role, even though the managers knew she was pregnant. She got the job and was given a year off on maternity leave - the job was held open for her.
"She was really blown away by the encouragement she received."
One of the major difficulties encountered by all working mothers is the restrictions on the time spent with their children.
"Working mums aren't often able to attend school camps or watch every sports game."
But Muller thinks there are ways to work around this.
"Make sure you are there for the most important things," she says. "Your children will be disappointed that you can't do everything, but when you do attend their events they will be even more special for them."
She tries to schedule at least two days a fortnight for children's activities - committing to these days will ensure your children they can count on you for at least a weekly event.
Muller advises mothers looking for work after having time off for children to look into the culture of the company they are working for.
She says companies with bad reputations in this area are unlikely to change, so it's best to avoid applying for positions there.
"If they aren't going to offer you support, the job will be doomed from the beginning," she says.
She says employment conditions are often better for mothers in professional service industries such as law or accountancy, but she says discrimination against working mothers is still happening all the time.
While she admits that there are times when being a working mother is undoubtedly challenging, she is happy to be providing a good, capable female role model for her children.
"There was one instance that really solidified how right it was for me to be a working mum.
"One of my daughters did a PowerPoint presentation of what her parents did.
"In the presentation she said that she was so proud of what a hard-working mother she had.
"By me working I've undermined the stereotypes about traditional male and female roles, and this is so important for girls growing up in the 21st century."
