Are you sure you're not projecting fears onto other gymgoers/staff?
If so, have you looked into other gym options? I wouldn't want to go to the gym at all if I felt like I wasn't welcome there...
This.
I've belonged to several gyms as a fit person, and as a fat person. I've never had people be rude or judgey to me, especially staff. My point is, if they really are being rude or mean or whatever, switch gyms! You pay to go there, you deserve respect. But if it's actually more of a projection thing, maybe that's just something to work on.
I actually don't think she should switch gyms. If these girls are giving you that unwelcoming vibe just ignore them and play on. I have had people try to make me feel uncomfortable in the gym setting before(not really because of weight but for other reasons) and I just cranked up my music louder, held my head higher and ran my heart out on the treadmill. They will get use to me and if not, oh well. I deserve to be anywhere I want and so do you.
Bear in mind that even if the occasional gym goer is looking down on you, someone else may be impressed by you. There was a woman that went to my last gym that probably was pushing 500 lbs. She wore a type of big dress to work out in. And you know what? I had SO much respect for her. I wanted to tell her so, but I was afraid my comment would make her self-conscious so I never did but she was amazing to me because she was in there to make a difference in her health and probably had some insecurities like what you have. Do it for you, and ignore anyone who's being a jerk about it.
Tonight was my second night at the gym. I was afraid of feeling judged, but I really haven't noticed it yet. For the most part, people just tend to be in their own world. I actually had an older woman compliment me tonight for actually using the equipment because apparently most women just do cardio.
When I go to the gym, I really don't focus on anyone; and it seems like no one focuses on me either. I had the occasional guy check me out (whether he's looking at me because I'm overweight or he likes what he sees, I have no idea) but I just ignore it. From the months that I have been going to the gym, I haven't had any negative connotations from other people. But it may be just me choosing to ignore those people. I am a very observant person, but I choose to overlook those pig headed people who think they are better than everyone.